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android_kernel_samsung_msm8976/block/bfq-iosched.c

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/*
* Budget Fair Queueing (BFQ) disk scheduler.
*
* Based on ideas and code from CFQ:
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
*
* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
* Paolo Valente <paolo.valente@unimore.it>
*
* Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
*
* Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ
* file.
*
* BFQ is a proportional-share storage-I/O scheduling algorithm based on
* the slice-by-slice service scheme of CFQ. But BFQ assigns budgets,
* measured in number of sectors, to processes instead of time slices. The
* device is not granted to the in-service process for a given time slice,
* but until it has exhausted its assigned budget. This change from the time
* to the service domain allows BFQ to distribute the device throughput
* among processes as desired, without any distortion due to ZBR, workload
* fluctuations or other factors. BFQ uses an ad hoc internal scheduler,
* called B-WF2Q+, to schedule processes according to their budgets. More
* precisely, BFQ schedules queues associated to processes. Thanks to the
* accurate policy of B-WF2Q+, BFQ can afford to assign high budgets to
* I/O-bound processes issuing sequential requests (to boost the
* throughput), and yet guarantee a low latency to interactive and soft
* real-time applications.
*
* BFQ is described in [1], where also a reference to the initial, more
* theoretical paper on BFQ can be found. The interested reader can find
* in the latter paper full details on the main algorithm, as well as
* formulas of the guarantees and formal proofs of all the properties.
* With respect to the version of BFQ presented in these papers, this
* implementation adds a few more heuristics, such as the one that
* guarantees a low latency to soft real-time applications, and a
* hierarchical extension based on H-WF2Q+.
*
* B-WF2Q+ is based on WF2Q+, that is described in [2], together with
* H-WF2Q+, while the augmented tree used to implement B-WF2Q+ with O(log N)
* complexity derives from the one introduced with EEVDF in [3].
*
* [1] P. Valente and M. Andreolini, ``Improving Application Responsiveness
* with the BFQ Disk I/O Scheduler'',
* Proceedings of the 5th Annual International Systems and Storage
* Conference (SYSTOR '12), June 2012.
*
* http://algogroup.unimo.it/people/paolo/disk_sched/bf1-v1-suite-results.pdf
*
* [2] Jon C.R. Bennett and H. Zhang, ``Hierarchical Packet Fair Queueing
* Algorithms,'' IEEE/ACM Transactions on Networking, 5(5):675-689,
* Oct 1997.
*
* http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz
*
* [3] I. Stoica and H. Abdel-Wahab, ``Earliest Eligible Virtual Deadline
* First: A Flexible and Accurate Mechanism for Proportional Share
* Resource Allocation,'' technical report.
*
* http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/cgroup.h>
#include <linux/elevator.h>
#include <linux/jiffies.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include "bfq.h"
#include "blk.h"
/* Expiration time of sync (0) and async (1) requests, in jiffies. */
static const int bfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
/* Maximum backwards seek, in KiB. */
static const int bfq_back_max = 16 * 1024;
/* Penalty of a backwards seek, in number of sectors. */
static const int bfq_back_penalty = 2;
/* Idling period duration, in jiffies. */
static int bfq_slice_idle = HZ / 125;
/* Default maximum budget values, in sectors and number of requests. */
static const int bfq_default_max_budget = 16 * 1024;
static const int bfq_max_budget_async_rq = 4;
/*
* Async to sync throughput distribution is controlled as follows:
* when an async request is served, the entity is charged the number
* of sectors of the request, multiplied by the factor below
*/
static const int bfq_async_charge_factor = 10;
/* Default timeout values, in jiffies, approximating CFQ defaults. */
static const int bfq_timeout_sync = HZ / 8;
static int bfq_timeout_async = HZ / 25;
struct kmem_cache *bfq_pool;
/* Below this threshold (in ms), we consider thinktime immediate. */
#define BFQ_MIN_TT 2
/* hw_tag detection: parallel requests threshold and min samples needed. */
#define BFQ_HW_QUEUE_THRESHOLD 4
#define BFQ_HW_QUEUE_SAMPLES 32
#define BFQQ_SEEK_THR (sector_t)(8 * 1024)
#define BFQQ_SEEKY(bfqq) ((bfqq)->seek_mean > BFQQ_SEEK_THR)
/* Min samples used for peak rate estimation (for autotuning). */
#define BFQ_PEAK_RATE_SAMPLES 32
/* Shift used for peak rate fixed precision calculations. */
#define BFQ_RATE_SHIFT 16
/*
* By default, BFQ computes the duration of the weight raising for
* interactive applications automatically, using the following formula:
* duration = (R / r) * T, where r is the peak rate of the device, and
* R and T are two reference parameters.
* In particular, R is the peak rate of the reference device (see below),
* and T is a reference time: given the systems that are likely to be
* installed on the reference device according to its speed class, T is
* about the maximum time needed, under BFQ and while reading two files in
* parallel, to load typical large applications on these systems.
* In practice, the slower/faster the device at hand is, the more/less it
* takes to load applications with respect to the reference device.
* Accordingly, the longer/shorter BFQ grants weight raising to interactive
* applications.
*
* BFQ uses four different reference pairs (R, T), depending on:
* . whether the device is rotational or non-rotational;
* . whether the device is slow, such as old or portable HDDs, as well as
* SD cards, or fast, such as newer HDDs and SSDs.
*
* The device's speed class is dynamically (re)detected in
* bfq_update_peak_rate() every time the estimated peak rate is updated.
*
* In the following definitions, R_slow[0]/R_fast[0] and T_slow[0]/T_fast[0]
* are the reference values for a slow/fast rotational device, whereas
* R_slow[1]/R_fast[1] and T_slow[1]/T_fast[1] are the reference values for
* a slow/fast non-rotational device. Finally, device_speed_thresh are the
* thresholds used to switch between speed classes.
* Both the reference peak rates and the thresholds are measured in
* sectors/usec, left-shifted by BFQ_RATE_SHIFT.
*/
static int R_slow[2] = {1536, 10752};
static int R_fast[2] = {17415, 34791};
/*
* To improve readability, a conversion function is used to initialize the
* following arrays, which entails that they can be initialized only in a
* function.
*/
static int T_slow[2];
static int T_fast[2];
static int device_speed_thresh[2];
#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \
{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0])
#define RQ_BFQQ(rq) ((rq)->elv.priv[1])
static inline void bfq_schedule_dispatch(struct bfq_data *bfqd);
#include "bfq-ioc.c"
#include "bfq-sched.c"
#include "bfq-cgroup.c"
#define bfq_class_idle(bfqq) ((bfqq)->entity.ioprio_class ==\
IOPRIO_CLASS_IDLE)
#define bfq_class_rt(bfqq) ((bfqq)->entity.ioprio_class ==\
IOPRIO_CLASS_RT)
#define bfq_sample_valid(samples) ((samples) > 80)
/*
* The following macro groups conditions that need to be evaluated when
* checking if existing queues and groups form a symmetric scenario
* and therefore idling can be reduced or disabled for some of the
* queues. See the comment to the function bfq_bfqq_must_not_expire()
* for further details.
*/
#ifdef CONFIG_CGROUP_BFQIO
#define symmetric_scenario (!bfqd->active_numerous_groups && \
!bfq_differentiated_weights(bfqd))
#else
#define symmetric_scenario (!bfq_differentiated_weights(bfqd))
#endif
/*
* We regard a request as SYNC, if either it's a read or has the SYNC bit
* set (in which case it could also be a direct WRITE).
*/
static inline int bfq_bio_sync(struct bio *bio)
{
if (bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC))
return 1;
return 0;
}
/*
* Scheduler run of queue, if there are requests pending and no one in the
* driver that will restart queueing.
*/
static inline void bfq_schedule_dispatch(struct bfq_data *bfqd)
{
if (bfqd->queued != 0) {
bfq_log(bfqd, "schedule dispatch");
kblockd_schedule_work(bfqd->queue, &bfqd->unplug_work);
}
}
/*
* Lifted from AS - choose which of rq1 and rq2 that is best served now.
* We choose the request that is closesr to the head right now. Distance
* behind the head is penalized and only allowed to a certain extent.
*/
static struct request *bfq_choose_req(struct bfq_data *bfqd,
struct request *rq1,
struct request *rq2,
sector_t last)
{
sector_t s1, s2, d1 = 0, d2 = 0;
unsigned long back_max;
#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */
#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */
unsigned wrap = 0; /* bit mask: requests behind the disk head? */
if (rq1 == NULL || rq1 == rq2)
return rq2;
if (rq2 == NULL)
return rq1;
if (rq_is_sync(rq1) && !rq_is_sync(rq2))
return rq1;
else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
return rq2;
if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
return rq1;
else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META))
return rq2;
s1 = blk_rq_pos(rq1);
s2 = blk_rq_pos(rq2);
/*
* By definition, 1KiB is 2 sectors.
*/
back_max = bfqd->bfq_back_max * 2;
/*
* Strict one way elevator _except_ in the case where we allow
* short backward seeks which are biased as twice the cost of a
* similar forward seek.
*/
if (s1 >= last)
d1 = s1 - last;
else if (s1 + back_max >= last)
d1 = (last - s1) * bfqd->bfq_back_penalty;
else
wrap |= BFQ_RQ1_WRAP;
if (s2 >= last)
d2 = s2 - last;
else if (s2 + back_max >= last)
d2 = (last - s2) * bfqd->bfq_back_penalty;
else
wrap |= BFQ_RQ2_WRAP;
/* Found required data */
/*
* By doing switch() on the bit mask "wrap" we avoid having to
* check two variables for all permutations: --> faster!
*/
switch (wrap) {
case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
if (d1 < d2)
return rq1;
else if (d2 < d1)
return rq2;
else {
if (s1 >= s2)
return rq1;
else
return rq2;
}
case BFQ_RQ2_WRAP:
return rq1;
case BFQ_RQ1_WRAP:
return rq2;
case (BFQ_RQ1_WRAP|BFQ_RQ2_WRAP): /* both rqs wrapped */
default:
/*
* Since both rqs are wrapped,
* start with the one that's further behind head
* (--> only *one* back seek required),
* since back seek takes more time than forward.
*/
if (s1 <= s2)
return rq1;
else
return rq2;
}
}
static struct bfq_queue *
bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root,
sector_t sector, struct rb_node **ret_parent,
struct rb_node ***rb_link)
{
struct rb_node **p, *parent;
struct bfq_queue *bfqq = NULL;
parent = NULL;
p = &root->rb_node;
while (*p) {
struct rb_node **n;
parent = *p;
bfqq = rb_entry(parent, struct bfq_queue, pos_node);
/*
* Sort strictly based on sector. Smallest to the left,
* largest to the right.
*/
if (sector > blk_rq_pos(bfqq->next_rq))
n = &(*p)->rb_right;
else if (sector < blk_rq_pos(bfqq->next_rq))
n = &(*p)->rb_left;
else
break;
p = n;
bfqq = NULL;
}
*ret_parent = parent;
if (rb_link)
*rb_link = p;
bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d",
(long long unsigned)sector,
bfqq != NULL ? bfqq->pid : 0);
return bfqq;
}
static void bfq_rq_pos_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct rb_node **p, *parent;
struct bfq_queue *__bfqq;
if (bfqq->pos_root != NULL) {
rb_erase(&bfqq->pos_node, bfqq->pos_root);
bfqq->pos_root = NULL;
}
if (bfq_class_idle(bfqq))
return;
if (!bfqq->next_rq)
return;
bfqq->pos_root = &bfqd->rq_pos_tree;
__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
blk_rq_pos(bfqq->next_rq), &parent, &p);
if (__bfqq == NULL) {
rb_link_node(&bfqq->pos_node, parent, p);
rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
} else
bfqq->pos_root = NULL;
}
/*
* Tell whether there are active queues or groups with differentiated weights.
*/
static inline bool bfq_differentiated_weights(struct bfq_data *bfqd)
{
/*
* For weights to differ, at least one of the trees must contain
* at least two nodes.
*/
return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) &&
(bfqd->queue_weights_tree.rb_node->rb_left ||
bfqd->queue_weights_tree.rb_node->rb_right)
#ifdef CONFIG_CGROUP_BFQIO
) ||
(!RB_EMPTY_ROOT(&bfqd->group_weights_tree) &&
(bfqd->group_weights_tree.rb_node->rb_left ||
bfqd->group_weights_tree.rb_node->rb_right)
#endif
);
}
/*
* If the weight-counter tree passed as input contains no counter for
* the weight of the input entity, then add that counter; otherwise just
* increment the existing counter.
*
* Note that weight-counter trees contain few nodes in mostly symmetric
* scenarios. For example, if all queues have the same weight, then the
* weight-counter tree for the queues may contain at most one node.
* This holds even if low_latency is on, because weight-raised queues
* are not inserted in the tree.
* In most scenarios, the rate at which nodes are created/destroyed
* should be low too.
*/
static void bfq_weights_tree_add(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
/*
* Do not insert if the entity is already associated with a
* counter, which happens if:
* 1) the entity is associated with a queue,
* 2) a request arrival has caused the queue to become both
* non-weight-raised, and hence change its weight, and
* backlogged; in this respect, each of the two events
* causes an invocation of this function,
* 3) this is the invocation of this function caused by the
* second event. This second invocation is actually useless,
* and we handle this fact by exiting immediately. More
* efficient or clearer solutions might possibly be adopted.
*/
if (entity->weight_counter)
return;
while (*new) {
struct bfq_weight_counter *__counter = container_of(*new,
struct bfq_weight_counter,
weights_node);
parent = *new;
if (entity->weight == __counter->weight) {
entity->weight_counter = __counter;
goto inc_counter;
}
if (entity->weight < __counter->weight)
new = &((*new)->rb_left);
else
new = &((*new)->rb_right);
}
entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter),
GFP_ATOMIC);
entity->weight_counter->weight = entity->weight;
rb_link_node(&entity->weight_counter->weights_node, parent, new);
rb_insert_color(&entity->weight_counter->weights_node, root);
inc_counter:
entity->weight_counter->num_active++;
}
/*
* Decrement the weight counter associated with the entity, and, if the
* counter reaches 0, remove the counter from the tree.
* See the comments to the function bfq_weights_tree_add() for considerations
* about overhead.
*/
static void bfq_weights_tree_remove(struct bfq_data *bfqd,
struct bfq_entity *entity,
struct rb_root *root)
{
if (!entity->weight_counter)
return;
BUG_ON(RB_EMPTY_ROOT(root));
BUG_ON(entity->weight_counter->weight != entity->weight);
BUG_ON(!entity->weight_counter->num_active);
entity->weight_counter->num_active--;
if (entity->weight_counter->num_active > 0)
goto reset_entity_pointer;
rb_erase(&entity->weight_counter->weights_node, root);
kfree(entity->weight_counter);
reset_entity_pointer:
entity->weight_counter = NULL;
}
static struct request *bfq_find_next_rq(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
struct request *last)
{
struct rb_node *rbnext = rb_next(&last->rb_node);
struct rb_node *rbprev = rb_prev(&last->rb_node);
struct request *next = NULL, *prev = NULL;
BUG_ON(RB_EMPTY_NODE(&last->rb_node));
if (rbprev != NULL)
prev = rb_entry_rq(rbprev);
if (rbnext != NULL)
next = rb_entry_rq(rbnext);
else {
rbnext = rb_first(&bfqq->sort_list);
if (rbnext && rbnext != &last->rb_node)
next = rb_entry_rq(rbnext);
}
return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last));
}
/* see the definition of bfq_async_charge_factor for details */
static inline unsigned long bfq_serv_to_charge(struct request *rq,
struct bfq_queue *bfqq)
{
return blk_rq_sectors(rq) *
(1 + ((!bfq_bfqq_sync(bfqq)) * (bfqq->wr_coeff == 1) *
bfq_async_charge_factor));
}
/**
* bfq_updated_next_req - update the queue after a new next_rq selection.
* @bfqd: the device data the queue belongs to.
* @bfqq: the queue to update.
*
* If the first request of a queue changes we make sure that the queue
* has enough budget to serve at least its first request (if the
* request has grown). We do this because if the queue has not enough
* budget for its first request, it has to go through two dispatch
* rounds to actually get it dispatched.
*/
static void bfq_updated_next_req(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
struct request *next_rq = bfqq->next_rq;
unsigned long new_budget;
if (next_rq == NULL)
return;
if (bfqq == bfqd->in_service_queue)
/*
* In order not to break guarantees, budgets cannot be
* changed after an entity has been selected.
*/
return;
BUG_ON(entity->tree != &st->active);
BUG_ON(entity == entity->sched_data->in_service_entity);
new_budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq));
if (entity->budget != new_budget) {
entity->budget = new_budget;
bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
new_budget);
bfq_activate_bfqq(bfqd, bfqq);
}
}
static inline unsigned int bfq_wr_duration(struct bfq_data *bfqd)
{
u64 dur;
if (bfqd->bfq_wr_max_time > 0)
return bfqd->bfq_wr_max_time;
dur = bfqd->RT_prod;
do_div(dur, bfqd->peak_rate);
return dur;
}
static inline unsigned
bfq_bfqq_cooperations(struct bfq_queue *bfqq)
{
return bfqq->bic ? bfqq->bic->cooperations : 0;
}
static inline void
bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
{
if (bic->saved_idle_window)
bfq_mark_bfqq_idle_window(bfqq);
else
bfq_clear_bfqq_idle_window(bfqq);
if (bic->saved_IO_bound)
bfq_mark_bfqq_IO_bound(bfqq);
else
bfq_clear_bfqq_IO_bound(bfqq);
/* Assuming that the flag in_large_burst is already correctly set */
if (bic->wr_time_left && bfqq->bfqd->low_latency &&
!bfq_bfqq_in_large_burst(bfqq) &&
bic->cooperations < bfqq->bfqd->bfq_coop_thresh) {
/*
* Start a weight raising period with the duration given by
* the raising_time_left snapshot.
*/
if (bfq_bfqq_busy(bfqq))
bfqq->bfqd->wr_busy_queues++;
bfqq->wr_coeff = bfqq->bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bic->wr_time_left;
bfqq->last_wr_start_finish = jiffies;
bfqq->entity.ioprio_changed = 1;
}
/*
* Clear wr_time_left to prevent bfq_bfqq_save_state() from
* getting confused about the queue's need of a weight-raising
* period.
*/
bic->wr_time_left = 0;
}
/* Must be called with the queue_lock held. */
static int bfqq_process_refs(struct bfq_queue *bfqq)
{
int process_refs, io_refs;
io_refs = bfqq->allocated[READ] + bfqq->allocated[WRITE];
process_refs = atomic_read(&bfqq->ref) - io_refs - bfqq->entity.on_st;
BUG_ON(process_refs < 0);
return process_refs;
}
/* Empty burst list and add just bfqq (see comments to bfq_handle_burst) */
static inline void bfq_reset_burst_list(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
struct bfq_queue *item;
struct hlist_node *n;
hlist_for_each_entry_safe(item, n, &bfqd->burst_list, burst_list_node)
hlist_del_init(&item->burst_list_node);
hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
bfqd->burst_size = 1;
}
/* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */
static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
/* Increment burst size to take into account also bfqq */
bfqd->burst_size++;
if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) {
struct bfq_queue *pos, *bfqq_item;
struct hlist_node *n;
/*
* Enough queues have been activated shortly after each
* other to consider this burst as large.
*/
bfqd->large_burst = true;
/*
* We can now mark all queues in the burst list as
* belonging to a large burst.
*/
hlist_for_each_entry(bfqq_item, &bfqd->burst_list,
burst_list_node)
bfq_mark_bfqq_in_large_burst(bfqq_item);
bfq_mark_bfqq_in_large_burst(bfqq);
/*
* From now on, and until the current burst finishes, any
* new queue being activated shortly after the last queue
* was inserted in the burst can be immediately marked as
* belonging to a large burst. So the burst list is not
* needed any more. Remove it.
*/
hlist_for_each_entry_safe(pos, n, &bfqd->burst_list,
burst_list_node)
hlist_del_init(&pos->burst_list_node);
} else /* burst not yet large: add bfqq to the burst list */
hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
}
/*
* If many queues happen to become active shortly after each other, then,
* to help the processes associated to these queues get their job done as
* soon as possible, it is usually better to not grant either weight-raising
* or device idling to these queues. In this comment we describe, firstly,
* the reasons why this fact holds, and, secondly, the next function, which
* implements the main steps needed to properly mark these queues so that
* they can then be treated in a different way.
*
* As for the terminology, we say that a queue becomes active, i.e.,
* switches from idle to backlogged, either when it is created (as a
* consequence of the arrival of an I/O request), or, if already existing,
* when a new request for the queue arrives while the queue is idle.
* Bursts of activations, i.e., activations of different queues occurring
* shortly after each other, are typically caused by services or applications
* that spawn or reactivate many parallel threads/processes. Examples are
* systemd during boot or git grep.
*
* These services or applications benefit mostly from a high throughput:
* the quicker the requests of the activated queues are cumulatively served,
* the sooner the target job of these queues gets completed. As a consequence,
* weight-raising any of these queues, which also implies idling the device
* for it, is almost always counterproductive: in most cases it just lowers
* throughput.
*
* On the other hand, a burst of activations may be also caused by the start
* of an application that does not consist in a lot of parallel I/O-bound
* threads. In fact, with a complex application, the burst may be just a
* consequence of the fact that several processes need to be executed to
* start-up the application. To start an application as quickly as possible,
* the best thing to do is to privilege the I/O related to the application
* with respect to all other I/O. Therefore, the best strategy to start as
* quickly as possible an application that causes a burst of activations is
* to weight-raise all the queues activated during the burst. This is the
* exact opposite of the best strategy for the other type of bursts.
*
* In the end, to take the best action for each of the two cases, the two
* types of bursts need to be distinguished. Fortunately, this seems
* relatively easy to do, by looking at the sizes of the bursts. In
* particular, we found a threshold such that bursts with a larger size
* than that threshold are apparently caused only by services or commands
* such as systemd or git grep. For brevity, hereafter we call just 'large'
* these bursts. BFQ *does not* weight-raise queues whose activations occur
* in a large burst. In addition, for each of these queues BFQ performs or
* does not perform idling depending on which choice boosts the throughput
* most. The exact choice depends on the device and request pattern at
* hand.
*
* Turning back to the next function, it implements all the steps needed
* to detect the occurrence of a large burst and to properly mark all the
* queues belonging to it (so that they can then be treated in a different
* way). This goal is achieved by maintaining a special "burst list" that
* holds, temporarily, the queues that belong to the burst in progress. The
* list is then used to mark these queues as belonging to a large burst if
* the burst does become large. The main steps are the following.
*
* . when the very first queue is activated, the queue is inserted into the
* list (as it could be the first queue in a possible burst)
*
* . if the current burst has not yet become large, and a queue Q that does
* not yet belong to the burst is activated shortly after the last time
* at which a new queue entered the burst list, then the function appends
* Q to the burst list
*
* . if, as a consequence of the previous step, the burst size reaches
* the large-burst threshold, then
*
* . all the queues in the burst list are marked as belonging to a
* large burst
*
* . the burst list is deleted; in fact, the burst list already served
* its purpose (keeping temporarily track of the queues in a burst,
* so as to be able to mark them as belonging to a large burst in the
* previous sub-step), and now is not needed any more
*
* . the device enters a large-burst mode
*
* . if a queue Q that does not belong to the burst is activated while
* the device is in large-burst mode and shortly after the last time
* at which a queue either entered the burst list or was marked as
* belonging to the current large burst, then Q is immediately marked
* as belonging to a large burst.
*
* . if a queue Q that does not belong to the burst is activated a while
* later, i.e., not shortly after, than the last time at which a queue
* either entered the burst list or was marked as belonging to the
* current large burst, then the current burst is deemed as finished and:
*
* . the large-burst mode is reset if set
*
* . the burst list is emptied
*
* . Q is inserted in the burst list, as Q may be the first queue
* in a possible new burst (then the burst list contains just Q
* after this step).
*/
static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bool idle_for_long_time)
{
/*
* If bfqq happened to be activated in a burst, but has been idle
* for at least as long as an interactive queue, then we assume
* that, in the overall I/O initiated in the burst, the I/O
* associated to bfqq is finished. So bfqq does not need to be
* treated as a queue belonging to a burst anymore. Accordingly,
* we reset bfqq's in_large_burst flag if set, and remove bfqq
* from the burst list if it's there. We do not decrement instead
* burst_size, because the fact that bfqq does not need to belong
* to the burst list any more does not invalidate the fact that
* bfqq may have been activated during the current burst.
*/
if (idle_for_long_time) {
hlist_del_init(&bfqq->burst_list_node);
bfq_clear_bfqq_in_large_burst(bfqq);
}
/*
* If bfqq is already in the burst list or is part of a large
* burst, then there is nothing else to do.
*/
if (!hlist_unhashed(&bfqq->burst_list_node) ||
bfq_bfqq_in_large_burst(bfqq))
return;
/*
* If bfqq's activation happens late enough, then the current
* burst is finished, and related data structures must be reset.
*
* In this respect, consider the special case where bfqq is the very
* first queue being activated. In this case, last_ins_in_burst is
* not yet significant when we get here. But it is easy to verify
* that, whether or not the following condition is true, bfqq will
* end up being inserted into the burst list. In particular the
* list will happen to contain only bfqq. And this is exactly what
* has to happen, as bfqq may be the first queue in a possible
* burst.
*/
if (time_is_before_jiffies(bfqd->last_ins_in_burst +
bfqd->bfq_burst_interval)) {
bfqd->large_burst = false;
bfq_reset_burst_list(bfqd, bfqq);
return;
}
/*
* If we get here, then bfqq is being activated shortly after the
* last queue. So, if the current burst is also large, we can mark
* bfqq as belonging to this large burst immediately.
*/
if (bfqd->large_burst) {
bfq_mark_bfqq_in_large_burst(bfqq);
return;
}
/*
* If we get here, then a large-burst state has not yet been
* reached, but bfqq is being activated shortly after the last
* queue. Then we add bfqq to the burst.
*/
bfq_add_to_burst(bfqd, bfqq);
}
static void bfq_add_request(struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_entity *entity = &bfqq->entity;
struct bfq_data *bfqd = bfqq->bfqd;
struct request *next_rq, *prev;
unsigned long old_wr_coeff = bfqq->wr_coeff;
bool interactive = false;
bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq));
bfqq->queued[rq_is_sync(rq)]++;
bfqd->queued++;
elv_rb_add(&bfqq->sort_list, rq);
/*
* Check if this request is a better next-serve candidate.
*/
prev = bfqq->next_rq;
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position);
BUG_ON(next_rq == NULL);
bfqq->next_rq = next_rq;
/*
* Adjust priority tree position, if next_rq changes.
*/
if (prev != bfqq->next_rq)
bfq_rq_pos_tree_add(bfqd, bfqq);
if (!bfq_bfqq_busy(bfqq)) {
bool soft_rt, coop_or_in_burst,
idle_for_long_time = time_is_before_jiffies(
bfqq->budget_timeout +
bfqd->bfq_wr_min_idle_time);
if (bfq_bfqq_sync(bfqq)) {
bool already_in_burst =
!hlist_unhashed(&bfqq->burst_list_node) ||
bfq_bfqq_in_large_burst(bfqq);
bfq_handle_burst(bfqd, bfqq, idle_for_long_time);
/*
* If bfqq was not already in the current burst,
* then, at this point, bfqq either has been
* added to the current burst or has caused the
* current burst to terminate. In particular, in
* the second case, bfqq has become the first
* queue in a possible new burst.
* In both cases last_ins_in_burst needs to be
* moved forward.
*/
if (!already_in_burst)
bfqd->last_ins_in_burst = jiffies;
}
coop_or_in_burst = bfq_bfqq_in_large_burst(bfqq) ||
bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh;
soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
!coop_or_in_burst &&
time_is_before_jiffies(bfqq->soft_rt_next_start);
interactive = !coop_or_in_burst && idle_for_long_time;
entity->budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq));
if (!bfq_bfqq_IO_bound(bfqq)) {
if (time_before(jiffies,
RQ_BIC(rq)->ttime.last_end_request +
bfqd->bfq_slice_idle)) {
bfqq->requests_within_timer++;
if (bfqq->requests_within_timer >=
bfqd->bfq_requests_within_timer)
bfq_mark_bfqq_IO_bound(bfqq);
} else
bfqq->requests_within_timer = 0;
}
if (!bfqd->low_latency)
goto add_bfqq_busy;
if (bfq_bfqq_just_split(bfqq))
goto set_ioprio_changed;
/*
* If the queue:
* - is not being boosted,
* - has been idle for enough time,
* - is not a sync queue or is linked to a bfq_io_cq (it is
* shared "for its nature" or it is not shared and its
* requests have not been redirected to a shared queue)
* start a weight-raising period.
*/
if (old_wr_coeff == 1 && (interactive || soft_rt) &&
(!bfq_bfqq_sync(bfqq) || bfqq->bic != NULL)) {
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
if (interactive)
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
else
bfqq->wr_cur_max_time =
bfqd->bfq_wr_rt_max_time;
bfq_log_bfqq(bfqd, bfqq,
"wrais starting at %lu, rais_max_time %u",
jiffies,
jiffies_to_msecs(bfqq->wr_cur_max_time));
} else if (old_wr_coeff > 1) {
if (interactive)
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
else if (coop_or_in_burst ||
(bfqq->wr_cur_max_time ==
bfqd->bfq_wr_rt_max_time &&
!soft_rt)) {
bfqq->wr_coeff = 1;
bfq_log_bfqq(bfqd, bfqq,
"wrais ending at %lu, rais_max_time %u",
jiffies,
jiffies_to_msecs(bfqq->
wr_cur_max_time));
} else if (time_before(
bfqq->last_wr_start_finish +
bfqq->wr_cur_max_time,
jiffies +
bfqd->bfq_wr_rt_max_time) &&
soft_rt) {
/*
*
* The remaining weight-raising time is lower
* than bfqd->bfq_wr_rt_max_time, which means
* that the application is enjoying weight
* raising either because deemed soft-rt in
* the near past, or because deemed interactive
* a long ago.
* In both cases, resetting now the current
* remaining weight-raising time for the
* application to the weight-raising duration
* for soft rt applications would not cause any
* latency increase for the application (as the
* new duration would be higher than the
* remaining time).
*
* In addition, the application is now meeting
* the requirements for being deemed soft rt.
* In the end we can correctly and safely
* (re)charge the weight-raising duration for
* the application with the weight-raising
* duration for soft rt applications.
*
* In particular, doing this recharge now, i.e.,
* before the weight-raising period for the
* application finishes, reduces the probability
* of the following negative scenario:
* 1) the weight of a soft rt application is
* raised at startup (as for any newly
* created application),
* 2) since the application is not interactive,
* at a certain time weight-raising is
* stopped for the application,
* 3) at that time the application happens to
* still have pending requests, and hence
* is destined to not have a chance to be
* deemed soft rt before these requests are
* completed (see the comments to the
* function bfq_bfqq_softrt_next_start()
* for details on soft rt detection),
* 4) these pending requests experience a high
* latency because the application is not
* weight-raised while they are pending.
*/
bfqq->last_wr_start_finish = jiffies;
bfqq->wr_cur_max_time =
bfqd->bfq_wr_rt_max_time;
}
}
set_ioprio_changed:
if (old_wr_coeff != bfqq->wr_coeff)
entity->ioprio_changed = 1;
add_bfqq_busy:
bfqq->last_idle_bklogged = jiffies;
bfqq->service_from_backlogged = 0;
bfq_clear_bfqq_softrt_update(bfqq);
bfq_add_bfqq_busy(bfqd, bfqq);
} else {
if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) &&
time_is_before_jiffies(
bfqq->last_wr_start_finish +
bfqd->bfq_wr_min_inter_arr_async)) {
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
bfqd->wr_busy_queues++;
entity->ioprio_changed = 1;
bfq_log_bfqq(bfqd, bfqq,
"non-idle wrais starting at %lu, rais_max_time %u",
jiffies,
jiffies_to_msecs(bfqq->wr_cur_max_time));
}
if (prev != bfqq->next_rq)
bfq_updated_next_req(bfqd, bfqq);
}
if (bfqd->low_latency &&
(old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive))
bfqq->last_wr_start_finish = jiffies;
}
static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd,
struct bio *bio)
{
struct task_struct *tsk = current;
struct bfq_io_cq *bic;
struct bfq_queue *bfqq;
bic = bfq_bic_lookup(bfqd, tsk->io_context);
if (bic == NULL)
return NULL;
bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio));
if (bfqq != NULL)
return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio));
return NULL;
}
static void bfq_activate_request(struct request_queue *q, struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
bfqd->rq_in_driver++;
bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
bfq_log(bfqd, "activate_request: new bfqd->last_position %llu",
(long long unsigned)bfqd->last_position);
}
static inline void bfq_deactivate_request(struct request_queue *q,
struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
BUG_ON(bfqd->rq_in_driver == 0);
bfqd->rq_in_driver--;
}
static void bfq_remove_request(struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd = bfqq->bfqd;
const int sync = rq_is_sync(rq);
if (bfqq->next_rq == rq) {
bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq);
bfq_updated_next_req(bfqd, bfqq);
}
if (rq->queuelist.prev != &rq->queuelist)
list_del_init(&rq->queuelist);
BUG_ON(bfqq->queued[sync] == 0);
bfqq->queued[sync]--;
bfqd->queued--;
elv_rb_del(&bfqq->sort_list, rq);
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue)
bfq_del_bfqq_busy(bfqd, bfqq, 1);
/*
* Remove queue from request-position tree as it is empty.
*/
if (bfqq->pos_root != NULL) {
rb_erase(&bfqq->pos_node, bfqq->pos_root);
bfqq->pos_root = NULL;
}
}
if (rq->cmd_flags & REQ_META) {
BUG_ON(bfqq->meta_pending == 0);
bfqq->meta_pending--;
}
}
static int bfq_merge(struct request_queue *q, struct request **req,
struct bio *bio)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct request *__rq;
__rq = bfq_find_rq_fmerge(bfqd, bio);
if (__rq != NULL && elv_rq_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_FRONT_MERGE;
}
return ELEVATOR_NO_MERGE;
}
static void bfq_merged_request(struct request_queue *q, struct request *req,
int type)
{
if (type == ELEVATOR_FRONT_MERGE &&
rb_prev(&req->rb_node) &&
blk_rq_pos(req) <
blk_rq_pos(container_of(rb_prev(&req->rb_node),
struct request, rb_node))) {
struct bfq_queue *bfqq = RQ_BFQQ(req);
struct bfq_data *bfqd = bfqq->bfqd;
struct request *prev, *next_rq;
/* Reposition request in its sort_list */
elv_rb_del(&bfqq->sort_list, req);
elv_rb_add(&bfqq->sort_list, req);
/* Choose next request to be served for bfqq */
prev = bfqq->next_rq;
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req,
bfqd->last_position);
BUG_ON(next_rq == NULL);
bfqq->next_rq = next_rq;
/*
* If next_rq changes, update both the queue's budget to
* fit the new request and the queue's position in its
* rq_pos_tree.
*/
if (prev != bfqq->next_rq) {
bfq_updated_next_req(bfqd, bfqq);
bfq_rq_pos_tree_add(bfqd, bfqq);
}
}
}
static void bfq_merged_requests(struct request_queue *q, struct request *rq,
struct request *next)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next);
/*
* If next and rq belong to the same bfq_queue and next is older
* than rq, then reposition rq in the fifo (by substituting next
* with rq). Otherwise, if next and rq belong to different
* bfq_queues, never reposition rq: in fact, we would have to
* reposition it with respect to next's position in its own fifo,
* which would most certainly be too expensive with respect to
* the benefits.
*/
if (bfqq == next_bfqq &&
!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
list_del_init(&rq->queuelist);
list_replace_init(&next->queuelist, &rq->queuelist);
rq_set_fifo_time(rq, rq_fifo_time(next));
}
if (bfqq->next_rq == next)
bfqq->next_rq = rq;
bfq_remove_request(next);
}
/* Must be called with bfqq != NULL */
static inline void bfq_bfqq_end_wr(struct bfq_queue *bfqq)
{
BUG_ON(bfqq == NULL);
if (bfq_bfqq_busy(bfqq))
bfqq->bfqd->wr_busy_queues--;
bfqq->wr_coeff = 1;
bfqq->wr_cur_max_time = 0;
/* Trigger a weight change on the next activation of the queue */
bfqq->entity.ioprio_changed = 1;
}
static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
struct bfq_group *bfqg)
{
int i, j;
for (i = 0; i < 2; i++)
for (j = 0; j < IOPRIO_BE_NR; j++)
if (bfqg->async_bfqq[i][j] != NULL)
bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
if (bfqg->async_idle_bfqq != NULL)
bfq_bfqq_end_wr(bfqg->async_idle_bfqq);
}
static void bfq_end_wr(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq;
spin_lock_irq(bfqd->queue->queue_lock);
list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list)
bfq_bfqq_end_wr(bfqq);
list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list)
bfq_bfqq_end_wr(bfqq);
bfq_end_wr_async(bfqd);
spin_unlock_irq(bfqd->queue->queue_lock);
}
static inline sector_t bfq_io_struct_pos(void *io_struct, bool request)
{
if (request)
return blk_rq_pos(io_struct);
else
return ((struct bio *)io_struct)->bi_sector;
}
static inline sector_t bfq_dist_from(sector_t pos1,
sector_t pos2)
{
if (pos1 >= pos2)
return pos1 - pos2;
else
return pos2 - pos1;
}
static inline int bfq_rq_close_to_sector(void *io_struct, bool request,
sector_t sector)
{
return bfq_dist_from(bfq_io_struct_pos(io_struct, request), sector) <=
BFQQ_SEEK_THR;
}
static struct bfq_queue *bfqq_close(struct bfq_data *bfqd, sector_t sector)
{
struct rb_root *root = &bfqd->rq_pos_tree;
struct rb_node *parent, *node;
struct bfq_queue *__bfqq;
if (RB_EMPTY_ROOT(root))
return NULL;
/*
* First, if we find a request starting at the end of the last
* request, choose it.
*/
__bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL);
if (__bfqq != NULL)
return __bfqq;
/*
* If the exact sector wasn't found, the parent of the NULL leaf
* will contain the closest sector (rq_pos_tree sorted by
* next_request position).
*/
__bfqq = rb_entry(parent, struct bfq_queue, pos_node);
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
return __bfqq;
if (blk_rq_pos(__bfqq->next_rq) < sector)
node = rb_next(&__bfqq->pos_node);
else
node = rb_prev(&__bfqq->pos_node);
if (node == NULL)
return NULL;
__bfqq = rb_entry(node, struct bfq_queue, pos_node);
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
return __bfqq;
return NULL;
}
/*
* bfqd - obvious
* cur_bfqq - passed in so that we don't decide that the current queue
* is closely cooperating with itself
* sector - used as a reference point to search for a close queue
*/
static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd,
struct bfq_queue *cur_bfqq,
sector_t sector)
{
struct bfq_queue *bfqq;
if (bfq_class_idle(cur_bfqq))
return NULL;
if (!bfq_bfqq_sync(cur_bfqq))
return NULL;
if (BFQQ_SEEKY(cur_bfqq))
return NULL;
/* If device has only one backlogged bfq_queue, don't search. */
if (bfqd->busy_queues == 1)
return NULL;
/*
* We should notice if some of the queues are cooperating, e.g.
* working closely on the same area of the disk. In that case,
* we can group them together and don't waste time idling.
*/
bfqq = bfqq_close(bfqd, sector);
if (bfqq == NULL || bfqq == cur_bfqq)
return NULL;
/*
* Do not merge queues from different bfq_groups.
*/
if (bfqq->entity.parent != cur_bfqq->entity.parent)
return NULL;
/*
* It only makes sense to merge sync queues.
*/
if (!bfq_bfqq_sync(bfqq))
return NULL;
if (BFQQ_SEEKY(bfqq))
return NULL;
/*
* Do not merge queues of different priority classes.
*/
if (bfq_class_rt(bfqq) != bfq_class_rt(cur_bfqq))
return NULL;
return bfqq;
}
static struct bfq_queue *
bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
{
int process_refs, new_process_refs;
struct bfq_queue *__bfqq;
/*
* If there are no process references on the new_bfqq, then it is
* unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
* may have dropped their last reference (not just their last process
* reference).
*/
if (!bfqq_process_refs(new_bfqq))
return NULL;
/* Avoid a circular list and skip interim queue merges. */
while ((__bfqq = new_bfqq->new_bfqq)) {
if (__bfqq == bfqq)
return NULL;
new_bfqq = __bfqq;
}
process_refs = bfqq_process_refs(bfqq);
new_process_refs = bfqq_process_refs(new_bfqq);
/*
* If the process for the bfqq has gone away, there is no
* sense in merging the queues.
*/
if (process_refs == 0 || new_process_refs == 0)
return NULL;
bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
new_bfqq->pid);
/*
* Merging is just a redirection: the requests of the process
* owning one of the two queues are redirected to the other queue.
* The latter queue, in its turn, is set as shared if this is the
* first time that the requests of some process are redirected to
* it.
*
* We redirect bfqq to new_bfqq and not the opposite, because we
* are in the context of the process owning bfqq, hence we have
* the io_cq of this process. So we can immediately configure this
* io_cq to redirect the requests of the process to new_bfqq.
*
* NOTE, even if new_bfqq coincides with the in-service queue, the
* io_cq of new_bfqq is not available, because, if the in-service
* queue is shared, bfqd->in_service_bic may not point to the
* io_cq of the in-service queue.
* Redirecting the requests of the process owning bfqq to the
* currently in-service queue is in any case the best option, as
* we feed the in-service queue with new requests close to the
* last request served and, by doing so, hopefully increase the
* throughput.
*/
bfqq->new_bfqq = new_bfqq;
atomic_add(process_refs, &new_bfqq->ref);
return new_bfqq;
}
/*
* Attempt to schedule a merge of bfqq with the currently in-service queue
* or with a close queue among the scheduled queues.
* Return NULL if no merge was scheduled, a pointer to the shared bfq_queue
* structure otherwise.
*
* The OOM queue is not allowed to participate to cooperation: in fact, since
* the requests temporarily redirected to the OOM queue could be redirected
* again to dedicated queues at any time, the state needed to correctly
* handle merging with the OOM queue would be quite complex and expensive
* to maintain. Besides, in such a critical condition as an out of memory,
* the benefits of queue merging may be little relevant, or even negligible.
*/
static struct bfq_queue *
bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
void *io_struct, bool request)
{
struct bfq_queue *in_service_bfqq, *new_bfqq;
if (bfqq->new_bfqq)
return bfqq->new_bfqq;
if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq))
return NULL;
in_service_bfqq = bfqd->in_service_queue;
if (in_service_bfqq == NULL || in_service_bfqq == bfqq ||
!bfqd->in_service_bic ||
unlikely(in_service_bfqq == &bfqd->oom_bfqq))
goto check_scheduled;
if (bfq_class_idle(in_service_bfqq) || bfq_class_idle(bfqq))
goto check_scheduled;
if (bfq_class_rt(in_service_bfqq) != bfq_class_rt(bfqq))
goto check_scheduled;
if (in_service_bfqq->entity.parent != bfqq->entity.parent)
goto check_scheduled;
if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) &&
bfq_bfqq_sync(in_service_bfqq) && bfq_bfqq_sync(bfqq)) {
new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq);
if (new_bfqq != NULL)
return new_bfqq; /* Merge with in-service queue */
}
/*
* Check whether there is a cooperator among currently scheduled
* queues. The only thing we need is that the bio/request is not
* NULL, as we need it to establish whether a cooperator exists.
*/
check_scheduled:
new_bfqq = bfq_close_cooperator(bfqd, bfqq,
bfq_io_struct_pos(io_struct, request));
if (new_bfqq && likely(new_bfqq != &bfqd->oom_bfqq))
return bfq_setup_merge(bfqq, new_bfqq);
return NULL;
}
static inline void
bfq_bfqq_save_state(struct bfq_queue *bfqq)
{
/*
* If bfqq->bic == NULL, the queue is already shared or its requests
* have already been redirected to a shared queue; both idle window
* and weight raising state have already been saved. Do nothing.
*/
if (bfqq->bic == NULL)
return;
if (bfqq->bic->wr_time_left)
/*
* This is the queue of a just-started process, and would
* deserve weight raising: we set wr_time_left to the full
* weight-raising duration to trigger weight-raising when
* and if the queue is split and the first request of the
* queue is enqueued.
*/
bfqq->bic->wr_time_left = bfq_wr_duration(bfqq->bfqd);
else if (bfqq->wr_coeff > 1) {
unsigned long wr_duration =
jiffies - bfqq->last_wr_start_finish;
/*
* It may happen that a queue's weight raising period lasts
* longer than its wr_cur_max_time, as weight raising is
* handled only when a request is enqueued or dispatched (it
* does not use any timer). If the weight raising period is
* about to end, don't save it.
*/
if (bfqq->wr_cur_max_time <= wr_duration)
bfqq->bic->wr_time_left = 0;
else
bfqq->bic->wr_time_left =
bfqq->wr_cur_max_time - wr_duration;
/*
* The bfq_queue is becoming shared or the requests of the
* process owning the queue are being redirected to a shared
* queue. Stop the weight raising period of the queue, as in
* both cases it should not be owned by an interactive or
* soft real-time application.
*/
bfq_bfqq_end_wr(bfqq);
} else
bfqq->bic->wr_time_left = 0;
bfqq->bic->saved_idle_window = bfq_bfqq_idle_window(bfqq);
bfqq->bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
bfqq->bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
bfqq->bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
bfqq->bic->cooperations++;
bfqq->bic->failed_cooperations = 0;
}
static inline void
bfq_get_bic_reference(struct bfq_queue *bfqq)
{
/*
* If bfqq->bic has a non-NULL value, the bic to which it belongs
* is about to begin using a shared bfq_queue.
*/
if (bfqq->bic)
atomic_long_inc(&bfqq->bic->icq.ioc->refcount);
}
static void
bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
{
bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
(long unsigned)new_bfqq->pid);
/* Save weight raising and idle window of the merged queues */
bfq_bfqq_save_state(bfqq);
bfq_bfqq_save_state(new_bfqq);
if (bfq_bfqq_IO_bound(bfqq))
bfq_mark_bfqq_IO_bound(new_bfqq);
bfq_clear_bfqq_IO_bound(bfqq);
/*
* Grab a reference to the bic, to prevent it from being destroyed
* before being possibly touched by a bfq_split_bfqq().
*/
bfq_get_bic_reference(bfqq);
bfq_get_bic_reference(new_bfqq);
/*
* Merge queues (that is, let bic redirect its requests to new_bfqq)
*/
bic_set_bfqq(bic, new_bfqq, 1);
bfq_mark_bfqq_coop(new_bfqq);
/*
* new_bfqq now belongs to at least two bics (it is a shared queue):
* set new_bfqq->bic to NULL. bfqq either:
* - does not belong to any bic any more, and hence bfqq->bic must
* be set to NULL, or
* - is a queue whose owning bics have already been redirected to a
* different queue, hence the queue is destined to not belong to
* any bic soon and bfqq->bic is already NULL (therefore the next
* assignment causes no harm).
*/
new_bfqq->bic = NULL;
bfqq->bic = NULL;
bfq_put_queue(bfqq);
}
static inline void bfq_bfqq_increase_failed_cooperations(struct bfq_queue *bfqq)
{
struct bfq_io_cq *bic = bfqq->bic;
struct bfq_data *bfqd = bfqq->bfqd;
if (bic && bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh) {
bic->failed_cooperations++;
if (bic->failed_cooperations >= bfqd->bfq_failed_cooperations)
bic->cooperations = 0;
}
}
static int bfq_allow_merge(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_io_cq *bic;
struct bfq_queue *bfqq, *new_bfqq;
/*
* Disallow merge of a sync bio into an async request.
*/
if (bfq_bio_sync(bio) && !rq_is_sync(rq))
return 0;
/*
* Lookup the bfqq that this bio will be queued with. Allow
* merge only if rq is queued there.
* Queue lock is held here.
*/
bic = bfq_bic_lookup(bfqd, current->io_context);
if (bic == NULL)
return 0;
bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio));
/*
* We take advantage of this function to perform an early merge
* of the queues of possible cooperating processes.
*/
if (bfqq != NULL) {
new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false);
if (new_bfqq != NULL) {
bfq_merge_bfqqs(bfqd, bic, bfqq, new_bfqq);
/*
* If we get here, the bio will be queued in the
* shared queue, i.e., new_bfqq, so use new_bfqq
* to decide whether bio and rq can be merged.
*/
bfqq = new_bfqq;
} else
bfq_bfqq_increase_failed_cooperations(bfqq);
}
return bfqq == RQ_BFQQ(rq);
}
static void __bfq_set_in_service_queue(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
if (bfqq != NULL) {
bfq_mark_bfqq_must_alloc(bfqq);
bfq_mark_bfqq_budget_new(bfqq);
bfq_clear_bfqq_fifo_expire(bfqq);
bfqd->budgets_assigned = (bfqd->budgets_assigned*7 + 256) / 8;
bfq_log_bfqq(bfqd, bfqq,
"set_in_service_queue, cur-budget = %lu",
bfqq->entity.budget);
}
bfqd->in_service_queue = bfqq;
}
/*
* Get and set a new queue for service.
*/
static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfq_get_next_queue(bfqd);
__bfq_set_in_service_queue(bfqd, bfqq);
return bfqq;
}
/*
* If enough samples have been computed, return the current max budget
* stored in bfqd, which is dynamically updated according to the
* estimated disk peak rate; otherwise return the default max budget
*/
static inline unsigned long bfq_max_budget(struct bfq_data *bfqd)
{
if (bfqd->budgets_assigned < 194)
return bfq_default_max_budget;
else
return bfqd->bfq_max_budget;
}
/*
* Return min budget, which is a fraction of the current or default
* max budget (trying with 1/32)
*/
static inline unsigned long bfq_min_budget(struct bfq_data *bfqd)
{
if (bfqd->budgets_assigned < 194)
return bfq_default_max_budget / 32;
else
return bfqd->bfq_max_budget / 32;
}
static void bfq_arm_slice_timer(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfqd->in_service_queue;
struct bfq_io_cq *bic;
unsigned long sl;
BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list));
/* Processes have exited, don't wait. */
bic = bfqd->in_service_bic;
if (bic == NULL || atomic_read(&bic->icq.ioc->active_ref) == 0)
return;
bfq_mark_bfqq_wait_request(bfqq);
/*
* We don't want to idle for seeks, but we do want to allow
* fair distribution of slice time for a process doing back-to-back
* seeks. So allow a little bit of time for him to submit a new rq.
*
* To prevent processes with (partly) seeky workloads from
* being too ill-treated, grant them a small fraction of the
* assigned budget before reducing the waiting time to
* BFQ_MIN_TT. This happened to help reduce latency.
*/
sl = bfqd->bfq_slice_idle;
/*
* Unless the queue is being weight-raised or the scenario is
* asymmetric, grant only minimum idle time if the queue either
* has been seeky for long enough or has already proved to be
* constantly seeky.
*/
if (bfq_sample_valid(bfqq->seek_samples) &&
((BFQQ_SEEKY(bfqq) && bfqq->entity.service >
bfq_max_budget(bfqq->bfqd) / 8) ||
bfq_bfqq_constantly_seeky(bfqq)) && bfqq->wr_coeff == 1 &&
symmetric_scenario)
sl = min(sl, msecs_to_jiffies(BFQ_MIN_TT));
else if (bfqq->wr_coeff > 1)
sl = sl * 3;
bfqd->last_idling_start = ktime_get();
mod_timer(&bfqd->idle_slice_timer, jiffies + sl);
bfq_log(bfqd, "arm idle: %u/%u ms",
jiffies_to_msecs(sl), jiffies_to_msecs(bfqd->bfq_slice_idle));
}
/*
* Set the maximum time for the in-service queue to consume its
* budget. This prevents seeky processes from lowering the disk
* throughput (always guaranteed with a time slice scheme as in CFQ).
*/
static void bfq_set_budget_timeout(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfqd->in_service_queue;
unsigned int timeout_coeff;
if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time)
timeout_coeff = 1;
else
timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight;
bfqd->last_budget_start = ktime_get();
bfq_clear_bfqq_budget_new(bfqq);
bfqq->budget_timeout = jiffies +
bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] * timeout_coeff;
bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u",
jiffies_to_msecs(bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] *
timeout_coeff));
}
/*
* Move request from internal lists to the request queue dispatch list.
*/
static void bfq_dispatch_insert(struct request_queue *q, struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_queue *bfqq = RQ_BFQQ(rq);
/*
* For consistency, the next instruction should have been executed
* after removing the request from the queue and dispatching it.
* We execute instead this instruction before bfq_remove_request()
* (and hence introduce a temporary inconsistency), for efficiency.
* In fact, in a forced_dispatch, this prevents two counters related
* to bfqq->dispatched to risk to be uselessly decremented if bfqq
* is not in service, and then to be incremented again after
* incrementing bfqq->dispatched.
*/
bfqq->dispatched++;
bfq_remove_request(rq);
elv_dispatch_sort(q, rq);
if (bfq_bfqq_sync(bfqq))
bfqd->sync_flight++;
}
/*
* Return expired entry, or NULL to just start from scratch in rbtree.
*/
static struct request *bfq_check_fifo(struct bfq_queue *bfqq)
{
struct request *rq = NULL;
if (bfq_bfqq_fifo_expire(bfqq))
return NULL;
bfq_mark_bfqq_fifo_expire(bfqq);
if (list_empty(&bfqq->fifo))
return NULL;
rq = rq_entry_fifo(bfqq->fifo.next);
if (time_before(jiffies, rq_fifo_time(rq)))
return NULL;
return rq;
}
static inline unsigned long bfq_bfqq_budget_left(struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
return entity->budget - entity->service;
}
static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
BUG_ON(bfqq != bfqd->in_service_queue);
__bfq_bfqd_reset_in_service(bfqd);
/*
* If this bfqq is shared between multiple processes, check
* to make sure that those processes are still issuing I/Os
* within the mean seek distance. If not, it may be time to
* break the queues apart again.
*/
if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq))
bfq_mark_bfqq_split_coop(bfqq);
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
/*
* Overloading budget_timeout field to store the time
* at which the queue remains with no backlog; used by
* the weight-raising mechanism.
*/
bfqq->budget_timeout = jiffies;
bfq_del_bfqq_busy(bfqd, bfqq, 1);
} else {
bfq_activate_bfqq(bfqd, bfqq);
/*
* Resort priority tree of potential close cooperators.
*/
bfq_rq_pos_tree_add(bfqd, bfqq);
}
}
/**
* __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior.
* @bfqd: device data.
* @bfqq: queue to update.
* @reason: reason for expiration.
*
* Handle the feedback on @bfqq budget. See the body for detailed
* comments.
*/
static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
enum bfqq_expiration reason)
{
struct request *next_rq;
unsigned long budget, min_budget;
budget = bfqq->max_budget;
min_budget = bfq_min_budget(bfqd);
BUG_ON(bfqq != bfqd->in_service_queue);
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %lu, budg left %lu",
bfqq->entity.budget, bfq_bfqq_budget_left(bfqq));
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %lu, min budg %lu",
budget, bfq_min_budget(bfqd));
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d",
bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue));
if (bfq_bfqq_sync(bfqq)) {
switch (reason) {
/*
* Caveat: in all the following cases we trade latency
* for throughput.
*/
case BFQ_BFQQ_TOO_IDLE:
/*
* This is the only case where we may reduce
* the budget: if there is no request of the
* process still waiting for completion, then
* we assume (tentatively) that the timer has
* expired because the batch of requests of
* the process could have been served with a
* smaller budget. Hence, betting that
* process will behave in the same way when it
* becomes backlogged again, we reduce its
* next budget. As long as we guess right,
* this budget cut reduces the latency
* experienced by the process.
*
* However, if there are still outstanding
* requests, then the process may have not yet
* issued its next request just because it is
* still waiting for the completion of some of
* the still outstanding ones. So in this
* subcase we do not reduce its budget, on the
* contrary we increase it to possibly boost
* the throughput, as discussed in the
* comments to the BUDGET_TIMEOUT case.
*/
if (bfqq->dispatched > 0) /* still outstanding reqs */
budget = min(budget * 2, bfqd->bfq_max_budget);
else {
if (budget > 5 * min_budget)
budget -= 4 * min_budget;
else
budget = min_budget;
}
break;
case BFQ_BFQQ_BUDGET_TIMEOUT:
/*
* We double the budget here because: 1) it
* gives the chance to boost the throughput if
* this is not a seeky process (which may have
* bumped into this timeout because of, e.g.,
* ZBR), 2) together with charge_full_budget
* it helps give seeky processes higher
* timestamps, and hence be served less
* frequently.
*/
budget = min(budget * 2, bfqd->bfq_max_budget);
break;
case BFQ_BFQQ_BUDGET_EXHAUSTED:
/*
* The process still has backlog, and did not
* let either the budget timeout or the disk
* idling timeout expire. Hence it is not
* seeky, has a short thinktime and may be
* happy with a higher budget too. So
* definitely increase the budget of this good
* candidate to boost the disk throughput.
*/
budget = min(budget * 4, bfqd->bfq_max_budget);
break;
case BFQ_BFQQ_NO_MORE_REQUESTS:
/*
* Leave the budget unchanged.
*/
default:
return;
}
} else /* async queue */
/* async queues get always the maximum possible budget
* (their ability to dispatch is limited by
* @bfqd->bfq_max_budget_async_rq).
*/
budget = bfqd->bfq_max_budget;
bfqq->max_budget = budget;
if (bfqd->budgets_assigned >= 194 && bfqd->bfq_user_max_budget == 0 &&
bfqq->max_budget > bfqd->bfq_max_budget)
bfqq->max_budget = bfqd->bfq_max_budget;
/*
* Make sure that we have enough budget for the next request.
* Since the finish time of the bfqq must be kept in sync with
* the budget, be sure to call __bfq_bfqq_expire() after the
* update.
*/
next_rq = bfqq->next_rq;
if (next_rq != NULL)
bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq));
else
bfqq->entity.budget = bfqq->max_budget;
bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %lu",
next_rq != NULL ? blk_rq_sectors(next_rq) : 0,
bfqq->entity.budget);
}
static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout)
{
unsigned long max_budget;
/*
* The max_budget calculated when autotuning is equal to the
* amount of sectors transfered in timeout_sync at the
* estimated peak rate.
*/
max_budget = (unsigned long)(peak_rate * 1000 *
timeout >> BFQ_RATE_SHIFT);
return max_budget;
}
/*
* In addition to updating the peak rate, checks whether the process
* is "slow", and returns 1 if so. This slow flag is used, in addition
* to the budget timeout, to reduce the amount of service provided to
* seeky processes, and hence reduce their chances to lower the
* throughput. See the code for more details.
*/
static int bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq,
int compensate, enum bfqq_expiration reason)
{
u64 bw, usecs, expected, timeout;
ktime_t delta;
int update = 0;
if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq))
return 0;
if (compensate)
delta = bfqd->last_idling_start;
else
delta = ktime_get();
delta = ktime_sub(delta, bfqd->last_budget_start);
usecs = ktime_to_us(delta);
/* Don't trust short/unrealistic values. */
if (usecs < 100 || usecs >= LONG_MAX)
return 0;
/*
* Calculate the bandwidth for the last slice. We use a 64 bit
* value to store the peak rate, in sectors per usec in fixed
* point math. We do so to have enough precision in the estimate
* and to avoid overflows.
*/
bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT;
do_div(bw, (unsigned long)usecs);
timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
/*
* Use only long (> 20ms) intervals to filter out spikes for
* the peak rate estimation.
*/
if (usecs > 20000) {
if (bw > bfqd->peak_rate ||
(!BFQQ_SEEKY(bfqq) &&
reason == BFQ_BFQQ_BUDGET_TIMEOUT)) {
bfq_log(bfqd, "measured bw =%llu", bw);
/*
* To smooth oscillations use a low-pass filter with
* alpha=7/8, i.e.,
* new_rate = (7/8) * old_rate + (1/8) * bw
*/
do_div(bw, 8);
if (bw == 0)
return 0;
bfqd->peak_rate *= 7;
do_div(bfqd->peak_rate, 8);
bfqd->peak_rate += bw;
update = 1;
bfq_log(bfqd, "new peak_rate=%llu", bfqd->peak_rate);
}
update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1;
if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES)
bfqd->peak_rate_samples++;
if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES &&
update) {
int dev_type = blk_queue_nonrot(bfqd->queue);
if (bfqd->bfq_user_max_budget == 0) {
bfqd->bfq_max_budget =
bfq_calc_max_budget(bfqd->peak_rate,
timeout);
bfq_log(bfqd, "new max_budget=%lu",
bfqd->bfq_max_budget);
}
if (bfqd->device_speed == BFQ_BFQD_FAST &&
bfqd->peak_rate < device_speed_thresh[dev_type]) {
bfqd->device_speed = BFQ_BFQD_SLOW;
bfqd->RT_prod = R_slow[dev_type] *
T_slow[dev_type];
} else if (bfqd->device_speed == BFQ_BFQD_SLOW &&
bfqd->peak_rate > device_speed_thresh[dev_type]) {
bfqd->device_speed = BFQ_BFQD_FAST;
bfqd->RT_prod = R_fast[dev_type] *
T_fast[dev_type];
}
}
}
/*
* If the process has been served for a too short time
* interval to let its possible sequential accesses prevail on
* the initial seek time needed to move the disk head on the
* first sector it requested, then give the process a chance
* and for the moment return false.
*/
if (bfqq->entity.budget <= bfq_max_budget(bfqd) / 8)
return 0;
/*
* A process is considered ``slow'' (i.e., seeky, so that we
* cannot treat it fairly in the service domain, as it would
* slow down too much the other processes) if, when a slice
* ends for whatever reason, it has received service at a
* rate that would not be high enough to complete the budget
* before the budget timeout expiration.
*/
expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT;
/*
* Caveat: processes doing IO in the slower disk zones will
* tend to be slow(er) even if not seeky. And the estimated
* peak rate will actually be an average over the disk
* surface. Hence, to not be too harsh with unlucky processes,
* we keep a budget/3 margin of safety before declaring a
* process slow.
*/
return expected > (4 * bfqq->entity.budget) / 3;
}
/*
* To be deemed as soft real-time, an application must meet two
* requirements. First, the application must not require an average
* bandwidth higher than the approximate bandwidth required to playback or
* record a compressed high-definition video.
* The next function is invoked on the completion of the last request of a
* batch, to compute the next-start time instant, soft_rt_next_start, such
* that, if the next request of the application does not arrive before
* soft_rt_next_start, then the above requirement on the bandwidth is met.
*
* The second requirement is that the request pattern of the application is
* isochronous, i.e., that, after issuing a request or a batch of requests,
* the application stops issuing new requests until all its pending requests
* have been completed. After that, the application may issue a new batch,
* and so on.
* For this reason the next function is invoked to compute
* soft_rt_next_start only for applications that meet this requirement,
* whereas soft_rt_next_start is set to infinity for applications that do
* not.
*
* Unfortunately, even a greedy application may happen to behave in an
* isochronous way if the CPU load is high. In fact, the application may
* stop issuing requests while the CPUs are busy serving other processes,
* then restart, then stop again for a while, and so on. In addition, if
* the disk achieves a low enough throughput with the request pattern
* issued by the application (e.g., because the request pattern is random
* and/or the device is slow), then the application may meet the above
* bandwidth requirement too. To prevent such a greedy application to be
* deemed as soft real-time, a further rule is used in the computation of
* soft_rt_next_start: soft_rt_next_start must be higher than the current
* time plus the maximum time for which the arrival of a request is waited
* for when a sync queue becomes idle, namely bfqd->bfq_slice_idle.
* This filters out greedy applications, as the latter issue instead their
* next request as soon as possible after the last one has been completed
* (in contrast, when a batch of requests is completed, a soft real-time
* application spends some time processing data).
*
* Unfortunately, the last filter may easily generate false positives if
* only bfqd->bfq_slice_idle is used as a reference time interval and one
* or both the following cases occur:
* 1) HZ is so low that the duration of a jiffy is comparable to or higher
* than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with
* HZ=100.
* 2) jiffies, instead of increasing at a constant rate, may stop increasing
* for a while, then suddenly 'jump' by several units to recover the lost
* increments. This seems to happen, e.g., inside virtual machines.
* To address this issue, we do not use as a reference time interval just
* bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In
* particular we add the minimum number of jiffies for which the filter
* seems to be quite precise also in embedded systems and KVM/QEMU virtual
* machines.
*/
static inline unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
return max(bfqq->last_idle_bklogged +
HZ * bfqq->service_from_backlogged /
bfqd->bfq_wr_max_softrt_rate,
jiffies + bfqq->bfqd->bfq_slice_idle + 4);
}
/*
* Return the largest-possible time instant such that, for as long as possible,
* the current time will be lower than this time instant according to the macro
* time_is_before_jiffies().
*/
static inline unsigned long bfq_infinity_from_now(unsigned long now)
{
return now + ULONG_MAX / 2;
}
/**
* bfq_bfqq_expire - expire a queue.
* @bfqd: device owning the queue.
* @bfqq: the queue to expire.
* @compensate: if true, compensate for the time spent idling.
* @reason: the reason causing the expiration.
*
*
* If the process associated to the queue is slow (i.e., seeky), or in
* case of budget timeout, or, finally, if it is async, we
* artificially charge it an entire budget (independently of the
* actual service it received). As a consequence, the queue will get
* higher timestamps than the correct ones upon reactivation, and
* hence it will be rescheduled as if it had received more service
* than what it actually received. In the end, this class of processes
* will receive less service in proportion to how slowly they consume
* their budgets (and hence how seriously they tend to lower the
* throughput).
*
* In contrast, when a queue expires because it has been idling for
* too much or because it exhausted its budget, we do not touch the
* amount of service it has received. Hence when the queue will be
* reactivated and its timestamps updated, the latter will be in sync
* with the actual service received by the queue until expiration.
*
* Charging a full budget to the first type of queues and the exact
* service to the others has the effect of using the WF2Q+ policy to
* schedule the former on a timeslice basis, without violating the
* service domain guarantees of the latter.
*/
static void bfq_bfqq_expire(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
int compensate,
enum bfqq_expiration reason)
{
int slow;
BUG_ON(bfqq != bfqd->in_service_queue);
/* Update disk peak rate for autotuning and check whether the
* process is slow (see bfq_update_peak_rate).
*/
slow = bfq_update_peak_rate(bfqd, bfqq, compensate, reason);
/*
* As above explained, 'punish' slow (i.e., seeky), timed-out
* and async queues, to favor sequential sync workloads.
*
* Processes doing I/O in the slower disk zones will tend to be
* slow(er) even if not seeky. Hence, since the estimated peak
* rate is actually an average over the disk surface, these
* processes may timeout just for bad luck. To avoid punishing
* them we do not charge a full budget to a process that
* succeeded in consuming at least 2/3 of its budget.
*/
if (slow || (reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3))
bfq_bfqq_charge_full_budget(bfqq);
bfqq->service_from_backlogged += bfqq->entity.service;
if (BFQQ_SEEKY(bfqq) && reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
!bfq_bfqq_constantly_seeky(bfqq)) {
bfq_mark_bfqq_constantly_seeky(bfqq);
if (!blk_queue_nonrot(bfqd->queue))
bfqd->const_seeky_busy_in_flight_queues++;
}
if (reason == BFQ_BFQQ_TOO_IDLE &&
bfqq->entity.service <= 2 * bfqq->entity.budget / 10 )
bfq_clear_bfqq_IO_bound(bfqq);
if (bfqd->low_latency && bfqq->wr_coeff == 1)
bfqq->last_wr_start_finish = jiffies;
if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 &&
RB_EMPTY_ROOT(&bfqq->sort_list)) {
/*
* If we get here, and there are no outstanding requests,
* then the request pattern is isochronous (see the comments
* to the function bfq_bfqq_softrt_next_start()). Hence we
* can compute soft_rt_next_start. If, instead, the queue
* still has outstanding requests, then we have to wait
* for the completion of all the outstanding requests to
* discover whether the request pattern is actually
* isochronous.
*/
if (bfqq->dispatched == 0)
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);
else {
/*
* The application is still waiting for the
* completion of one or more requests:
* prevent it from possibly being incorrectly
* deemed as soft real-time by setting its
* soft_rt_next_start to infinity. In fact,
* without this assignment, the application
* would be incorrectly deemed as soft
* real-time if:
* 1) it issued a new request before the
* completion of all its in-flight
* requests, and
* 2) at that time, its soft_rt_next_start
* happened to be in the past.
*/
bfqq->soft_rt_next_start =
bfq_infinity_from_now(jiffies);
/*
* Schedule an update of soft_rt_next_start to when
* the task may be discovered to be isochronous.
*/
bfq_mark_bfqq_softrt_update(bfqq);
}
}
bfq_log_bfqq(bfqd, bfqq,
"expire (%d, slow %d, num_disp %d, idle_win %d)", reason,
slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq));
/*
* Increase, decrease or leave budget unchanged according to
* reason.
*/
__bfq_bfqq_recalc_budget(bfqd, bfqq, reason);
__bfq_bfqq_expire(bfqd, bfqq);
}
/*
* Budget timeout is not implemented through a dedicated timer, but
* just checked on request arrivals and completions, as well as on
* idle timer expirations.
*/
static int bfq_bfqq_budget_timeout(struct bfq_queue *bfqq)
{
if (bfq_bfqq_budget_new(bfqq) ||
time_before(jiffies, bfqq->budget_timeout))
return 0;
return 1;
}
/*
* If we expire a queue that is waiting for the arrival of a new
* request, we may prevent the fictitious timestamp back-shifting that
* allows the guarantees of the queue to be preserved (see [1] for
* this tricky aspect). Hence we return true only if this condition
* does not hold, or if the queue is slow enough to deserve only to be
* kicked off for preserving a high throughput.
*/
static inline int bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq)
{
bfq_log_bfqq(bfqq->bfqd, bfqq,
"may_budget_timeout: wait_request %d left %d timeout %d",
bfq_bfqq_wait_request(bfqq),
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3,
bfq_bfqq_budget_timeout(bfqq));
return (!bfq_bfqq_wait_request(bfqq) ||
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3)
&&
bfq_bfqq_budget_timeout(bfqq);
}
/*
* Device idling is allowed only for the queues for which this function
* returns true. For this reason, the return value of this function plays a
* critical role for both throughput boosting and service guarantees. The
* return value is computed through a logical expression. In this rather
* long comment, we try to briefly describe all the details and motivations
* behind the components of this logical expression.
*
* First, the expression is false if bfqq is not sync, or if: bfqq happened
* to become active during a large burst of queue activations, and the
* pattern of requests bfqq contains boosts the throughput if bfqq is
* expired. In fact, queues that became active during a large burst benefit
* only from throughput, as discussed in the comments to bfq_handle_burst.
* In this respect, expiring bfqq certainly boosts the throughput on NCQ-
* capable flash-based devices, whereas, on rotational devices, it boosts
* the throughput only if bfqq contains random requests.
*
* On the opposite end, if (a) bfqq is sync, (b) the above burst-related
* condition does not hold, and (c) bfqq is being weight-raised, then the
* expression always evaluates to true, as device idling is instrumental
* for preserving low-latency guarantees (see [1]). If, instead, conditions
* (a) and (b) do hold, but (c) does not, then the expression evaluates to
* true only if: (1) bfqq is I/O-bound and has a non-null idle window, and
* (2) at least one of the following two conditions holds.
* The first condition is that the device is not performing NCQ, because
* idling the device most certainly boosts the throughput if this condition
* holds and bfqq is I/O-bound and has been granted a non-null idle window.
* The second compound condition is made of the logical AND of two components.
*
* The first component is true only if there is no weight-raised busy
* queue. This guarantees that the device is not idled for a sync non-
* weight-raised queue when there are busy weight-raised queues. The former
* is then expired immediately if empty. Combined with the timestamping
* rules of BFQ (see [1] for details), this causes sync non-weight-raised
* queues to get a lower number of requests served, and hence to ask for a
* lower number of requests from the request pool, before the busy weight-
* raised queues get served again.
*
* This is beneficial for the processes associated with weight-raised
* queues, when the request pool is saturated (e.g., in the presence of
* write hogs). In fact, if the processes associated with the other queues
* ask for requests at a lower rate, then weight-raised processes have a
* higher probability to get a request from the pool immediately (or at
* least soon) when they need one. Hence they have a higher probability to
* actually get a fraction of the disk throughput proportional to their
* high weight. This is especially true with NCQ-capable drives, which
* enqueue several requests in advance and further reorder internally-
* queued requests.
*
* In the end, mistreating non-weight-raised queues when there are busy
* weight-raised queues seems to mitigate starvation problems in the
* presence of heavy write workloads and NCQ, and hence to guarantee a
* higher application and system responsiveness in these hostile scenarios.
*
* If the first component of the compound condition is instead true, i.e.,
* there is no weight-raised busy queue, then the second component of the
* compound condition takes into account service-guarantee and throughput
* issues related to NCQ (recall that the compound condition is evaluated
* only if the device is detected as supporting NCQ).
*
* As for service guarantees, allowing the drive to enqueue more than one
* request at a time, and hence delegating de facto final scheduling
* decisions to the drive's internal scheduler, causes loss of control on
* the actual request service order. In this respect, when the drive is
* allowed to enqueue more than one request at a time, the service
* distribution enforced by the drive's internal scheduler is likely to
* coincide with the desired device-throughput distribution only in the
* following, perfectly symmetric, scenario:
* 1) all active queues have the same weight,
* 2) all active groups at the same level in the groups tree have the same
* weight,
* 3) all active groups at the same level in the groups tree have the same
* number of children.
*
* Even in such a scenario, sequential I/O may still receive a preferential
* treatment, but this is not likely to be a big issue with flash-based
* devices, because of their non-dramatic loss of throughput with random
* I/O. Things do differ with HDDs, for which additional care is taken, as
* explained after completing the discussion for flash-based devices.
*
* Unfortunately, keeping the necessary state for evaluating exactly the
* above symmetry conditions would be quite complex and time-consuming.
* Therefore BFQ evaluates instead the following stronger sub-conditions,
* for which it is much easier to maintain the needed state:
* 1) all active queues have the same weight,
* 2) all active groups have the same weight,
* 3) all active groups have at most one active child each.
* In particular, the last two conditions are always true if hierarchical
* support and the cgroups interface are not enabled, hence no state needs
* to be maintained in this case.
*
* According to the above considerations, the second component of the
* compound condition evaluates to true if any of the above symmetry
* sub-condition does not hold, or the device is not flash-based. Therefore,
* if also the first component is true, then idling is allowed for a sync
* queue. These are the only sub-conditions considered if the device is
* flash-based, as, for such a device, it is sensible to force idling only
* for service-guarantee issues. In fact, as for throughput, idling
* NCQ-capable flash-based devices would not boost the throughput even
* with sequential I/O; rather it would lower the throughput in proportion
* to how fast the device is. In the end, (only) if all the three
* sub-conditions hold and the device is flash-based, the compound
* condition evaluates to false and therefore no idling is performed.
*
* As already said, things change with a rotational device, where idling
* boosts the throughput with sequential I/O (even with NCQ). Hence, for
* such a device the second component of the compound condition evaluates
* to true also if the following additional sub-condition does not hold:
* the queue is constantly seeky. Unfortunately, this different behavior
* with respect to flash-based devices causes an additional asymmetry: if
* some sync queues enjoy idling and some other sync queues do not, then
* the latter get a low share of the device throughput, simply because the
* former get many requests served after being set as in service, whereas
* the latter do not. As a consequence, to guarantee the desired throughput
* distribution, on HDDs the compound expression evaluates to true (and
* hence device idling is performed) also if the following last symmetry
* condition does not hold: no other queue is benefiting from idling. Also
* this last condition is actually replaced with a simpler-to-maintain and
* stronger condition: there is no busy queue which is not constantly seeky
* (and hence may also benefit from idling).
*
* To sum up, when all the required symmetry and throughput-boosting
* sub-conditions hold, the second component of the compound condition
* evaluates to false, and hence no idling is performed. This helps to
* keep the drives' internal queues full on NCQ-capable devices, and hence
* to boost the throughput, without causing 'almost' any loss of service
* guarantees. The 'almost' follows from the fact that, if the internal
* queue of one such device is filled while all the sub-conditions hold,
* but at some point in time some sub-condition stops to hold, then it may
* become impossible to let requests be served in the new desired order
* until all the requests already queued in the device have been served.
*/
static inline bool bfq_bfqq_must_not_expire(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
#define cond_for_seeky_on_ncq_hdd (bfq_bfqq_constantly_seeky(bfqq) && \
bfqd->busy_in_flight_queues == \
bfqd->const_seeky_busy_in_flight_queues)
#define cond_for_expiring_in_burst (bfq_bfqq_in_large_burst(bfqq) && \
bfqd->hw_tag && \
(blk_queue_nonrot(bfqd->queue) || \
bfq_bfqq_constantly_seeky(bfqq)))
/*
* Condition for expiring a non-weight-raised queue (and hence not idling
* the device).
*/
#define cond_for_expiring_non_wr (bfqd->hw_tag && \
(bfqd->wr_busy_queues > 0 || \
(blk_queue_nonrot(bfqd->queue) || \
cond_for_seeky_on_ncq_hdd)))
return bfq_bfqq_sync(bfqq) &&
!cond_for_expiring_in_burst &&
(bfqq->wr_coeff > 1 || !symmetric_scenario ||
(bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_idle_window(bfqq) &&
!cond_for_expiring_non_wr)
);
}
/*
* If the in-service queue is empty but sync, and the function
* bfq_bfqq_must_not_expire returns true, then:
* 1) the queue must remain in service and cannot be expired, and
* 2) the disk must be idled to wait for the possible arrival of a new
* request for the queue.
* See the comments to the function bfq_bfqq_must_not_expire for the reasons
* why performing device idling is the best choice to boost the throughput
* and preserve service guarantees when bfq_bfqq_must_not_expire itself
* returns true.
*/
static inline bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 &&
bfq_bfqq_must_not_expire(bfqq);
}
/*
* Select a queue for service. If we have a current queue in service,
* check whether to continue servicing it, or retrieve and set a new one.
*/
static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq;
struct request *next_rq;
enum bfqq_expiration reason = BFQ_BFQQ_BUDGET_TIMEOUT;
bfqq = bfqd->in_service_queue;
if (bfqq == NULL)
goto new_queue;
bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
if (bfq_may_expire_for_budg_timeout(bfqq) &&
!timer_pending(&bfqd->idle_slice_timer) &&
!bfq_bfqq_must_idle(bfqq))
goto expire;
next_rq = bfqq->next_rq;
/*
* If bfqq has requests queued and it has enough budget left to
* serve them, keep the queue, otherwise expire it.
*/
if (next_rq != NULL) {
if (bfq_serv_to_charge(next_rq, bfqq) >
bfq_bfqq_budget_left(bfqq)) {
reason = BFQ_BFQQ_BUDGET_EXHAUSTED;
goto expire;
} else {
/*
* The idle timer may be pending because we may
* not disable disk idling even when a new request
* arrives.
*/
if (timer_pending(&bfqd->idle_slice_timer)) {
/*
* If we get here: 1) at least a new request
* has arrived but we have not disabled the
* timer because the request was too small,
* 2) then the block layer has unplugged
* the device, causing the dispatch to be
* invoked.
*
* Since the device is unplugged, now the
* requests are probably large enough to
* provide a reasonable throughput.
* So we disable idling.
*/
bfq_clear_bfqq_wait_request(bfqq);
del_timer(&bfqd->idle_slice_timer);
}
goto keep_queue;
}
}
/*
* No requests pending. However, if the in-service queue is idling
* for a new request, or has requests waiting for a completion and
* may idle after their completion, then keep it anyway.
*/
if (timer_pending(&bfqd->idle_slice_timer) ||
(bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq))) {
bfqq = NULL;
goto keep_queue;
}
reason = BFQ_BFQQ_NO_MORE_REQUESTS;
expire:
bfq_bfqq_expire(bfqd, bfqq, 0, reason);
new_queue:
bfqq = bfq_set_in_service_queue(bfqd);
bfq_log(bfqd, "select_queue: new queue %d returned",
bfqq != NULL ? bfqq->pid : 0);
keep_queue:
return bfqq;
}
static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
struct bfq_entity *entity = &bfqq->entity;
if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */
bfq_log_bfqq(bfqd, bfqq,
"raising period dur %u/%u msec, old coeff %u, w %d(%d)",
jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
jiffies_to_msecs(bfqq->wr_cur_max_time),
bfqq->wr_coeff,
bfqq->entity.weight, bfqq->entity.orig_weight);
BUG_ON(bfqq != bfqd->in_service_queue && entity->weight !=
entity->orig_weight * bfqq->wr_coeff);
if (entity->ioprio_changed)
bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change");
/*
* If the queue was activated in a burst, or
* too much time has elapsed from the beginning
* of this weight-raising period, or the queue has
* exceeded the acceptable number of cooperations,
* then end weight raising.
*/
if (bfq_bfqq_in_large_burst(bfqq) ||
bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh ||
time_is_before_jiffies(bfqq->last_wr_start_finish +
bfqq->wr_cur_max_time)) {
bfqq->last_wr_start_finish = jiffies;
bfq_log_bfqq(bfqd, bfqq,
"wrais ending at %lu, rais_max_time %u",
bfqq->last_wr_start_finish,
jiffies_to_msecs(bfqq->wr_cur_max_time));
bfq_bfqq_end_wr(bfqq);
}
}
/* Update weight both if it must be raised and if it must be lowered */
if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1))
__bfq_entity_update_weight_prio(
bfq_entity_service_tree(entity),
entity);
}
/*
* Dispatch one request from bfqq, moving it to the request queue
* dispatch list.
*/
static int bfq_dispatch_request(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
int dispatched = 0;
struct request *rq;
unsigned long service_to_charge;
BUG_ON(RB_EMPTY_ROOT(&bfqq->sort_list));
/* Follow expired path, else get first next available. */
rq = bfq_check_fifo(bfqq);
if (rq == NULL)
rq = bfqq->next_rq;
service_to_charge = bfq_serv_to_charge(rq, bfqq);
if (service_to_charge > bfq_bfqq_budget_left(bfqq)) {
/*
* This may happen if the next rq is chosen in fifo order
* instead of sector order. The budget is properly
* dimensioned to be always sufficient to serve the next
* request only if it is chosen in sector order. The reason
* is that it would be quite inefficient and little useful
* to always make sure that the budget is large enough to
* serve even the possible next rq in fifo order.
* In fact, requests are seldom served in fifo order.
*
* Expire the queue for budget exhaustion, and make sure
* that the next act_budget is enough to serve the next
* request, even if it comes from the fifo expired path.
*/
bfqq->next_rq = rq;
/*
* Since this dispatch is failed, make sure that
* a new one will be performed
*/
if (!bfqd->rq_in_driver)
bfq_schedule_dispatch(bfqd);
goto expire;
}
/* Finally, insert request into driver dispatch list. */
bfq_bfqq_served(bfqq, service_to_charge);
bfq_dispatch_insert(bfqd->queue, rq);
bfq_update_wr_data(bfqd, bfqq);
bfq_log_bfqq(bfqd, bfqq,
"dispatched %u sec req (%llu), budg left %lu",
blk_rq_sectors(rq),
(long long unsigned)blk_rq_pos(rq),
bfq_bfqq_budget_left(bfqq));
dispatched++;
if (bfqd->in_service_bic == NULL) {
atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
bfqd->in_service_bic = RQ_BIC(rq);
}
if (bfqd->busy_queues > 1 && ((!bfq_bfqq_sync(bfqq) &&
dispatched >= bfqd->bfq_max_budget_async_rq) ||
bfq_class_idle(bfqq)))
goto expire;
return dispatched;
expire:
bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_EXHAUSTED);
return dispatched;
}
static int __bfq_forced_dispatch_bfqq(struct bfq_queue *bfqq)
{
int dispatched = 0;
while (bfqq->next_rq != NULL) {
bfq_dispatch_insert(bfqq->bfqd->queue, bfqq->next_rq);
dispatched++;
}
BUG_ON(!list_empty(&bfqq->fifo));
return dispatched;
}
/*
* Drain our current requests.
* Used for barriers and when switching io schedulers on-the-fly.
*/
static int bfq_forced_dispatch(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq, *n;
struct bfq_service_tree *st;
int dispatched = 0;
bfqq = bfqd->in_service_queue;
if (bfqq != NULL)
__bfq_bfqq_expire(bfqd, bfqq);
/*
* Loop through classes, and be careful to leave the scheduler
* in a consistent state, as feedback mechanisms and vtime
* updates cannot be disabled during the process.
*/
list_for_each_entry_safe(bfqq, n, &bfqd->active_list, bfqq_list) {
st = bfq_entity_service_tree(&bfqq->entity);
dispatched += __bfq_forced_dispatch_bfqq(bfqq);
bfqq->max_budget = bfq_max_budget(bfqd);
bfq_forget_idle(st);
}
BUG_ON(bfqd->busy_queues != 0);
return dispatched;
}
static int bfq_dispatch_requests(struct request_queue *q, int force)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_queue *bfqq;
int max_dispatch;
bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues);
if (bfqd->busy_queues == 0)
return 0;
if (unlikely(force))
return bfq_forced_dispatch(bfqd);
bfqq = bfq_select_queue(bfqd);
if (bfqq == NULL)
return 0;
if (bfq_class_idle(bfqq))
max_dispatch = 1;
if (!bfq_bfqq_sync(bfqq))
max_dispatch = bfqd->bfq_max_budget_async_rq;
if (!bfq_bfqq_sync(bfqq) && bfqq->dispatched >= max_dispatch) {
if (bfqd->busy_queues > 1)
return 0;
if (bfqq->dispatched >= 4 * max_dispatch)
return 0;
}
if (bfqd->sync_flight != 0 && !bfq_bfqq_sync(bfqq))
return 0;
bfq_clear_bfqq_wait_request(bfqq);
BUG_ON(timer_pending(&bfqd->idle_slice_timer));
if (!bfq_dispatch_request(bfqd, bfqq))
return 0;
bfq_log_bfqq(bfqd, bfqq, "dispatched %s request",
bfq_bfqq_sync(bfqq) ? "sync" : "async");
return 1;
}
/*
* Task holds one reference to the queue, dropped when task exits. Each rq
* in-flight on this queue also holds a reference, dropped when rq is freed.
*
* Queue lock must be held here.
*/
static void bfq_put_queue(struct bfq_queue *bfqq)
{
struct bfq_data *bfqd = bfqq->bfqd;
BUG_ON(atomic_read(&bfqq->ref) <= 0);
bfq_log_bfqq(bfqd, bfqq, "put_queue: %p %d", bfqq,
atomic_read(&bfqq->ref));
if (!atomic_dec_and_test(&bfqq->ref))
return;
BUG_ON(rb_first(&bfqq->sort_list) != NULL);
BUG_ON(bfqq->allocated[READ] + bfqq->allocated[WRITE] != 0);
BUG_ON(bfqq->entity.tree != NULL);
BUG_ON(bfq_bfqq_busy(bfqq));
BUG_ON(bfqd->in_service_queue == bfqq);
if (bfq_bfqq_sync(bfqq))
/*
* The fact that this queue is being destroyed does not
* invalidate the fact that this queue may have been
* activated during the current burst. As a consequence,
* although the queue does not exist anymore, and hence
* needs to be removed from the burst list if there,
* the burst size has not to be decremented.
*/
hlist_del_init(&bfqq->burst_list_node);
bfq_log_bfqq(bfqd, bfqq, "put_queue: %p freed", bfqq);
kmem_cache_free(bfq_pool, bfqq);
}
static void bfq_put_cooperator(struct bfq_queue *bfqq)
{
struct bfq_queue *__bfqq, *next;
/*
* If this queue was scheduled to merge with another queue, be
* sure to drop the reference taken on that queue (and others in
* the merge chain). See bfq_setup_merge and bfq_merge_bfqqs.
*/
__bfqq = bfqq->new_bfqq;
while (__bfqq) {
if (__bfqq == bfqq)
break;
next = __bfqq->new_bfqq;
bfq_put_queue(__bfqq);
__bfqq = next;
}
}
static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
{
if (bfqq == bfqd->in_service_queue) {
__bfq_bfqq_expire(bfqd, bfqq);
bfq_schedule_dispatch(bfqd);
}
bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq,
atomic_read(&bfqq->ref));
bfq_put_cooperator(bfqq);
bfq_put_queue(bfqq);
}
static inline void bfq_init_icq(struct io_cq *icq)
{
struct bfq_io_cq *bic = icq_to_bic(icq);
bic->ttime.last_end_request = jiffies;
/*
* A newly created bic indicates that the process has just
* started doing I/O, and is probably mapping into memory its
* executable and libraries: it definitely needs weight raising.
* There is however the possibility that the process performs,
* for a while, I/O close to some other process. EQM intercepts
* this behavior and may merge the queue corresponding to the
* process with some other queue, BEFORE the weight of the queue
* is raised. Merged queues are not weight-raised (they are assumed
* to belong to processes that benefit only from high throughput).
* If the merge is basically the consequence of an accident, then
* the queue will be split soon and will get back its old weight.
* It is then important to write down somewhere that this queue
* does need weight raising, even if it did not make it to get its
* weight raised before being merged. To this purpose, we overload
* the field raising_time_left and assign 1 to it, to mark the queue
* as needing weight raising.
*/
bic->wr_time_left = 1;
}
static void bfq_exit_icq(struct io_cq *icq)
{
struct bfq_io_cq *bic = icq_to_bic(icq);
struct bfq_data *bfqd = bic_to_bfqd(bic);
if (bic->bfqq[BLK_RW_ASYNC]) {
bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_ASYNC]);
bic->bfqq[BLK_RW_ASYNC] = NULL;
}
if (bic->bfqq[BLK_RW_SYNC]) {
/*
* If the bic is using a shared queue, put the reference
* taken on the io_context when the bic started using a
* shared bfq_queue.
*/
if (bfq_bfqq_coop(bic->bfqq[BLK_RW_SYNC]))
put_io_context(icq->ioc);
bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_SYNC]);
bic->bfqq[BLK_RW_SYNC] = NULL;
}
}
/*
* Update the entity prio values; note that the new values will not
* be used until the next (re)activation.
*/
static void bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
{
struct task_struct *tsk = current;
int ioprio_class;
ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
switch (ioprio_class) {
default:
dev_err(bfqq->bfqd->queue->backing_dev_info.dev,
"bfq: bad prio class %d\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
* No prio set, inherit CPU scheduling settings.
*/
bfqq->entity.new_ioprio = task_nice_ioprio(tsk);
bfqq->entity.new_ioprio_class = task_nice_ioclass(tsk);
break;
case IOPRIO_CLASS_RT:
bfqq->entity.new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
bfqq->entity.new_ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
bfqq->entity.new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
bfqq->entity.new_ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
bfqq->entity.new_ioprio_class = IOPRIO_CLASS_IDLE;
bfqq->entity.new_ioprio = 7;
bfq_clear_bfqq_idle_window(bfqq);
break;
}
if (bfqq->entity.new_ioprio < 0 ||
bfqq->entity.new_ioprio >= IOPRIO_BE_NR) {
printk(KERN_CRIT "bfq_set_next_ioprio_data: new_ioprio %d\n",
bfqq->entity.new_ioprio);
BUG();
}
bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->entity.new_ioprio);
bfqq->entity.ioprio_changed = 1;
}
static void bfq_check_ioprio_change(struct bfq_io_cq *bic)
{
struct bfq_data *bfqd;
struct bfq_queue *bfqq, *new_bfqq;
struct bfq_group *bfqg;
unsigned long uninitialized_var(flags);
int ioprio = bic->icq.ioc->ioprio;
bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data),
&flags);
/*
* This condition may trigger on a newly created bic, be sure to
* drop the lock before returning.
*/
if (unlikely(bfqd == NULL) || likely(bic->ioprio == ioprio))
goto out;
bic->ioprio = ioprio;
bfqq = bic->bfqq[BLK_RW_ASYNC];
if (bfqq != NULL) {
bfqg = container_of(bfqq->entity.sched_data, struct bfq_group,
sched_data);
new_bfqq = bfq_get_queue(bfqd, bfqg, BLK_RW_ASYNC, bic,
GFP_ATOMIC);
if (new_bfqq != NULL) {
bic->bfqq[BLK_RW_ASYNC] = new_bfqq;
bfq_log_bfqq(bfqd, bfqq,
"check_ioprio_change: bfqq %p %d",
bfqq, atomic_read(&bfqq->ref));
bfq_put_queue(bfqq);
}
}
bfqq = bic->bfqq[BLK_RW_SYNC];
if (bfqq != NULL)
bfq_set_next_ioprio_data(bfqq, bic);
out:
bfq_put_bfqd_unlock(bfqd, &flags);
}
static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_io_cq *bic, pid_t pid, int is_sync)
{
RB_CLEAR_NODE(&bfqq->entity.rb_node);
INIT_LIST_HEAD(&bfqq->fifo);
INIT_HLIST_NODE(&bfqq->burst_list_node);
atomic_set(&bfqq->ref, 0);
bfqq->bfqd = bfqd;
if (bic)
bfq_set_next_ioprio_data(bfqq, bic);
if (is_sync) {
if (!bfq_class_idle(bfqq))
bfq_mark_bfqq_idle_window(bfqq);
bfq_mark_bfqq_sync(bfqq);
}
bfq_mark_bfqq_IO_bound(bfqq);
/* Tentative initial value to trade off between thr and lat */
bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3;
bfqq->pid = pid;
bfqq->wr_coeff = 1;
bfqq->last_wr_start_finish = 0;
/*
* Set to the value for which bfqq will not be deemed as
* soft rt when it becomes backlogged.
*/
bfqq->soft_rt_next_start = bfq_infinity_from_now(jiffies);
}
static struct bfq_queue *bfq_find_alloc_queue(struct bfq_data *bfqd,
struct bfq_group *bfqg,
int is_sync,
struct bfq_io_cq *bic,
gfp_t gfp_mask)
{
struct bfq_queue *bfqq, *new_bfqq = NULL;
retry:
/* bic always exists here */
bfqq = bic_to_bfqq(bic, is_sync);
/*
* Always try a new alloc if we fall back to the OOM bfqq
* originally, since it should just be a temporary situation.
*/
if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) {
bfqq = NULL;
if (new_bfqq != NULL) {
bfqq = new_bfqq;
new_bfqq = NULL;
} else if (gfp_mask & __GFP_WAIT) {
spin_unlock_irq(bfqd->queue->queue_lock);
new_bfqq = kmem_cache_alloc_node(bfq_pool,
gfp_mask | __GFP_ZERO,
bfqd->queue->node);
spin_lock_irq(bfqd->queue->queue_lock);
if (new_bfqq != NULL)
goto retry;
} else {
bfqq = kmem_cache_alloc_node(bfq_pool,
gfp_mask | __GFP_ZERO,
bfqd->queue->node);
}
if (bfqq != NULL) {
bfq_init_bfqq(bfqd, bfqq, bic, current->pid,
is_sync);
bfq_init_entity(&bfqq->entity, bfqg);
bfq_log_bfqq(bfqd, bfqq, "allocated");
} else {
bfqq = &bfqd->oom_bfqq;
bfq_log_bfqq(bfqd, bfqq, "using oom bfqq");
}
}
if (new_bfqq != NULL)
kmem_cache_free(bfq_pool, new_bfqq);
return bfqq;
}
static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
struct bfq_group *bfqg,
int ioprio_class, int ioprio)
{
switch (ioprio_class) {
case IOPRIO_CLASS_RT:
return &bfqg->async_bfqq[0][ioprio];
case IOPRIO_CLASS_NONE:
ioprio = IOPRIO_NORM;
/* fall through */
case IOPRIO_CLASS_BE:
return &bfqg->async_bfqq[1][ioprio];
case IOPRIO_CLASS_IDLE:
return &bfqg->async_idle_bfqq;
default:
BUG();
}
}
static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
struct bfq_group *bfqg, int is_sync,
struct bfq_io_cq *bic, gfp_t gfp_mask)
{
const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
struct bfq_queue **async_bfqq = NULL;
struct bfq_queue *bfqq = NULL;
if (!is_sync) {
async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
ioprio);
bfqq = *async_bfqq;
}
if (bfqq == NULL)
bfqq = bfq_find_alloc_queue(bfqd, bfqg, is_sync, bic, gfp_mask);
/*
* Pin the queue now that it's allocated, scheduler exit will
* prune it.
*/
if (!is_sync && *async_bfqq == NULL) {
atomic_inc(&bfqq->ref);
bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d",
bfqq, atomic_read(&bfqq->ref));
*async_bfqq = bfqq;
}
atomic_inc(&bfqq->ref);
bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq,
atomic_read(&bfqq->ref));
return bfqq;
}
static void bfq_update_io_thinktime(struct bfq_data *bfqd,
struct bfq_io_cq *bic)
{
unsigned long elapsed = jiffies - bic->ttime.last_end_request;
unsigned long ttime = min(elapsed, 2UL * bfqd->bfq_slice_idle);
bic->ttime.ttime_samples = (7*bic->ttime.ttime_samples + 256) / 8;
bic->ttime.ttime_total = (7*bic->ttime.ttime_total + 256*ttime) / 8;
bic->ttime.ttime_mean = (bic->ttime.ttime_total + 128) /
bic->ttime.ttime_samples;
}
static void bfq_update_io_seektime(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
struct request *rq)
{
sector_t sdist;
u64 total;
if (bfqq->last_request_pos < blk_rq_pos(rq))
sdist = blk_rq_pos(rq) - bfqq->last_request_pos;
else
sdist = bfqq->last_request_pos - blk_rq_pos(rq);
/*
* Don't allow the seek distance to get too large from the
* odd fragment, pagein, etc.
*/
if (bfqq->seek_samples == 0) /* first request, not really a seek */
sdist = 0;
else if (bfqq->seek_samples <= 60) /* second & third seek */
sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*1024);
else
sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*64);
bfqq->seek_samples = (7*bfqq->seek_samples + 256) / 8;
bfqq->seek_total = (7*bfqq->seek_total + (u64)256*sdist) / 8;
total = bfqq->seek_total + (bfqq->seek_samples/2);
do_div(total, bfqq->seek_samples);
bfqq->seek_mean = (sector_t)total;
bfq_log_bfqq(bfqd, bfqq, "dist=%llu mean=%llu", (u64)sdist,
(u64)bfqq->seek_mean);
}
/*
* Disable idle window if the process thinks too long or seeks so much that
* it doesn't matter.
*/
static void bfq_update_idle_window(struct bfq_data *bfqd,
struct bfq_queue *bfqq,
struct bfq_io_cq *bic)
{
int enable_idle;
/* Don't idle for async or idle io prio class. */
if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq))
return;
/* Idle window just restored, statistics are meaningless. */
if (bfq_bfqq_just_split(bfqq))
return;
enable_idle = bfq_bfqq_idle_window(bfqq);
if (atomic_read(&bic->icq.ioc->active_ref) == 0 ||
bfqd->bfq_slice_idle == 0 ||
(bfqd->hw_tag && BFQQ_SEEKY(bfqq) &&
bfqq->wr_coeff == 1))
enable_idle = 0;
else if (bfq_sample_valid(bic->ttime.ttime_samples)) {
if (bic->ttime.ttime_mean > bfqd->bfq_slice_idle &&
bfqq->wr_coeff == 1)
enable_idle = 0;
else
enable_idle = 1;
}
bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d",
enable_idle);
if (enable_idle)
bfq_mark_bfqq_idle_window(bfqq);
else
bfq_clear_bfqq_idle_window(bfqq);
}
/*
* Called when a new fs request (rq) is added to bfqq. Check if there's
* something we should do about it.
*/
static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct request *rq)
{
struct bfq_io_cq *bic = RQ_BIC(rq);
if (rq->cmd_flags & REQ_META)
bfqq->meta_pending++;
bfq_update_io_thinktime(bfqd, bic);
bfq_update_io_seektime(bfqd, bfqq, rq);
if (!BFQQ_SEEKY(bfqq) && bfq_bfqq_constantly_seeky(bfqq)) {
bfq_clear_bfqq_constantly_seeky(bfqq);
if (!blk_queue_nonrot(bfqd->queue)) {
BUG_ON(!bfqd->const_seeky_busy_in_flight_queues);
bfqd->const_seeky_busy_in_flight_queues--;
}
}
if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 ||
!BFQQ_SEEKY(bfqq))
bfq_update_idle_window(bfqd, bfqq, bic);
bfq_clear_bfqq_just_split(bfqq);
bfq_log_bfqq(bfqd, bfqq,
"rq_enqueued: idle_window=%d (seeky %d, mean %llu)",
bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq),
(long long unsigned)bfqq->seek_mean);
bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) {
int small_req = bfqq->queued[rq_is_sync(rq)] == 1 &&
blk_rq_sectors(rq) < 32;
int budget_timeout = bfq_bfqq_budget_timeout(bfqq);
/*
* There is just this request queued: if the request
* is small and the queue is not to be expired, then
* just exit.
*
* In this way, if the disk is being idled to wait for
* a new request from the in-service queue, we avoid
* unplugging the device and committing the disk to serve
* just a small request. On the contrary, we wait for
* the block layer to decide when to unplug the device:
* hopefully, new requests will be merged to this one
* quickly, then the device will be unplugged and
* larger requests will be dispatched.
*/
if (small_req && !budget_timeout)
return;
/*
* A large enough request arrived, or the queue is to
* be expired: in both cases disk idling is to be
* stopped, so clear wait_request flag and reset
* timer.
*/
bfq_clear_bfqq_wait_request(bfqq);
del_timer(&bfqd->idle_slice_timer);
/*
* The queue is not empty, because a new request just
* arrived. Hence we can safely expire the queue, in
* case of budget timeout, without risking that the
* timestamps of the queue are not updated correctly.
* See [1] for more details.
*/
if (budget_timeout)
bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT);
/*
* Let the request rip immediately, or let a new queue be
* selected if bfqq has just been expired.
*/
__blk_run_queue(bfqd->queue);
}
}
static void bfq_insert_request(struct request_queue *q, struct request *rq)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_queue *bfqq = RQ_BFQQ(rq), *new_bfqq;
assert_spin_locked(bfqd->queue->queue_lock);
/*
* An unplug may trigger a requeue of a request from the device
* driver: make sure we are in process context while trying to
* merge two bfq_queues.
*/
if (!in_interrupt()) {
new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true);
if (new_bfqq != NULL) {
if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq)
new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1);
/*
* Release the request's reference to the old bfqq
* and make sure one is taken to the shared queue.
*/
new_bfqq->allocated[rq_data_dir(rq)]++;
bfqq->allocated[rq_data_dir(rq)]--;
atomic_inc(&new_bfqq->ref);
bfq_put_queue(bfqq);
if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq)
bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
bfqq, new_bfqq);
rq->elv.priv[1] = new_bfqq;
bfqq = new_bfqq;
} else
bfq_bfqq_increase_failed_cooperations(bfqq);
}
bfq_add_request(rq);
/*
* Here a newly-created bfq_queue has already started a weight-raising
* period: clear raising_time_left to prevent bfq_bfqq_save_state()
* from assigning it a full weight-raising period. See the detailed
* comments about this field in bfq_init_icq().
*/
if (bfqq->bic != NULL)
bfqq->bic->wr_time_left = 0;
rq_set_fifo_time(rq, jiffies + bfqd->bfq_fifo_expire[rq_is_sync(rq)]);
list_add_tail(&rq->queuelist, &bfqq->fifo);
bfq_rq_enqueued(bfqd, bfqq, rq);
}
static void bfq_update_hw_tag(struct bfq_data *bfqd)
{
bfqd->max_rq_in_driver = max(bfqd->max_rq_in_driver,
bfqd->rq_in_driver);
if (bfqd->hw_tag == 1)
return;
/*
* This sample is valid if the number of outstanding requests
* is large enough to allow a queueing behavior. Note that the
* sum is not exact, as it's not taking into account deactivated
* requests.
*/
if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD)
return;
if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
return;
bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD;
bfqd->max_rq_in_driver = 0;
bfqd->hw_tag_samples = 0;
}
static void bfq_completed_request(struct request_queue *q, struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
struct bfq_data *bfqd = bfqq->bfqd;
bool sync = bfq_bfqq_sync(bfqq);
bfq_log_bfqq(bfqd, bfqq, "completed one req with %u sects left (%d)",
blk_rq_sectors(rq), sync);
bfq_update_hw_tag(bfqd);
BUG_ON(!bfqd->rq_in_driver);
BUG_ON(!bfqq->dispatched);
bfqd->rq_in_driver--;
bfqq->dispatched--;
if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
bfq_weights_tree_remove(bfqd, &bfqq->entity,
&bfqd->queue_weights_tree);
if (!blk_queue_nonrot(bfqd->queue)) {
BUG_ON(!bfqd->busy_in_flight_queues);
bfqd->busy_in_flight_queues--;
if (bfq_bfqq_constantly_seeky(bfqq)) {
BUG_ON(!bfqd->
const_seeky_busy_in_flight_queues);
bfqd->const_seeky_busy_in_flight_queues--;
}
}
}
if (sync) {
bfqd->sync_flight--;
RQ_BIC(rq)->ttime.last_end_request = jiffies;
}
/*
* If we are waiting to discover whether the request pattern of the
* task associated with the queue is actually isochronous, and
* both requisites for this condition to hold are satisfied, then
* compute soft_rt_next_start (see the comments to the function
* bfq_bfqq_softrt_next_start()).
*/
if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
RB_EMPTY_ROOT(&bfqq->sort_list))
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);
/*
* If this is the in-service queue, check if it needs to be expired,
* or if we want to idle in case it has no pending requests.
*/
if (bfqd->in_service_queue == bfqq) {
if (bfq_bfqq_budget_new(bfqq))
bfq_set_budget_timeout(bfqd);
if (bfq_bfqq_must_idle(bfqq)) {
bfq_arm_slice_timer(bfqd);
goto out;
} else if (bfq_may_expire_for_budg_timeout(bfqq))
bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT);
else if (RB_EMPTY_ROOT(&bfqq->sort_list) &&
(bfqq->dispatched == 0 ||
!bfq_bfqq_must_not_expire(bfqq)))
bfq_bfqq_expire(bfqd, bfqq, 0,
BFQ_BFQQ_NO_MORE_REQUESTS);
}
if (!bfqd->rq_in_driver)
bfq_schedule_dispatch(bfqd);
out:
return;
}
static inline int __bfq_may_queue(struct bfq_queue *bfqq)
{
if (bfq_bfqq_wait_request(bfqq) && bfq_bfqq_must_alloc(bfqq)) {
bfq_clear_bfqq_must_alloc(bfqq);
return ELV_MQUEUE_MUST;
}
return ELV_MQUEUE_MAY;
}
static int bfq_may_queue(struct request_queue *q, int rw)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct task_struct *tsk = current;
struct bfq_io_cq *bic;
struct bfq_queue *bfqq;
/*
* Don't force setup of a queue from here, as a call to may_queue
* does not necessarily imply that a request actually will be
* queued. So just lookup a possibly existing queue, or return
* 'may queue' if that fails.
*/
bic = bfq_bic_lookup(bfqd, tsk->io_context);
if (bic == NULL)
return ELV_MQUEUE_MAY;
bfqq = bic_to_bfqq(bic, rw_is_sync(rw));
if (bfqq != NULL)
return __bfq_may_queue(bfqq);
return ELV_MQUEUE_MAY;
}
/*
* Queue lock held here.
*/
static void bfq_put_request(struct request *rq)
{
struct bfq_queue *bfqq = RQ_BFQQ(rq);
if (bfqq != NULL) {
const int rw = rq_data_dir(rq);
BUG_ON(!bfqq->allocated[rw]);
bfqq->allocated[rw]--;
rq->elv.priv[0] = NULL;
rq->elv.priv[1] = NULL;
bfq_log_bfqq(bfqq->bfqd, bfqq, "put_request %p, %d",
bfqq, atomic_read(&bfqq->ref));
bfq_put_queue(bfqq);
}
}
/*
* Returns NULL if a new bfqq should be allocated, or the old bfqq if this
* was the last process referring to said bfqq.
*/
static struct bfq_queue *
bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq)
{
bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue");
put_io_context(bic->icq.ioc);
if (bfqq_process_refs(bfqq) == 1) {
bfqq->pid = current->pid;
bfq_clear_bfqq_coop(bfqq);
bfq_clear_bfqq_split_coop(bfqq);
return bfqq;
}
bic_set_bfqq(bic, NULL, 1);
bfq_put_cooperator(bfqq);
bfq_put_queue(bfqq);
return NULL;
}
/*
* Allocate bfq data structures associated with this request.
*/
static int bfq_set_request(struct request_queue *q, struct request *rq,
struct bio *bio, gfp_t gfp_mask)
{
struct bfq_data *bfqd = q->elevator->elevator_data;
struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq);
const int rw = rq_data_dir(rq);
const int is_sync = rq_is_sync(rq);
struct bfq_queue *bfqq;
struct bfq_group *bfqg;
unsigned long flags;
bool split = false;
might_sleep_if(gfp_mask & __GFP_WAIT);
bfq_check_ioprio_change(bic);
spin_lock_irqsave(q->queue_lock, flags);
if (bic == NULL)
goto queue_fail;
bfqg = bfq_bic_update_cgroup(bic);
new_queue:
bfqq = bic_to_bfqq(bic, is_sync);
if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) {
bfqq = bfq_get_queue(bfqd, bfqg, is_sync, bic, gfp_mask);
bic_set_bfqq(bic, bfqq, is_sync);
if (split && is_sync) {
if ((bic->was_in_burst_list && bfqd->large_burst) ||
bic->saved_in_large_burst)
bfq_mark_bfqq_in_large_burst(bfqq);
else {
bfq_clear_bfqq_in_large_burst(bfqq);
if (bic->was_in_burst_list)
hlist_add_head(&bfqq->burst_list_node,
&bfqd->burst_list);
}
}
} else {
/* If the queue was seeky for too long, break it apart. */
if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) {
bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq");
bfqq = bfq_split_bfqq(bic, bfqq);
split = true;
if (!bfqq)
goto new_queue;
}
}
bfqq->allocated[rw]++;
atomic_inc(&bfqq->ref);
bfq_log_bfqq(bfqd, bfqq, "set_request: bfqq %p, %d", bfqq,
atomic_read(&bfqq->ref));
rq->elv.priv[0] = bic;
rq->elv.priv[1] = bfqq;
/*
* If a bfq_queue has only one process reference, it is owned
* by only one bfq_io_cq: we can set the bic field of the
* bfq_queue to the address of that structure. Also, if the
* queue has just been split, mark a flag so that the
* information is available to the other scheduler hooks.
*/
if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
bfqq->bic = bic;
if (split) {
bfq_mark_bfqq_just_split(bfqq);
/*
* If the queue has just been split from a shared
* queue, restore the idle window and the possible
* weight raising period.
*/
bfq_bfqq_resume_state(bfqq, bic);
}
}
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
queue_fail:
bfq_schedule_dispatch(bfqd);
spin_unlock_irqrestore(q->queue_lock, flags);
return 1;
}
static void bfq_kick_queue(struct work_struct *work)
{
struct bfq_data *bfqd =
container_of(work, struct bfq_data, unplug_work);
struct request_queue *q = bfqd->queue;
spin_lock_irq(q->queue_lock);
__blk_run_queue(q);
spin_unlock_irq(q->queue_lock);
}
/*
* Handler of the expiration of the timer running if the in-service queue
* is idling inside its time slice.
*/
static void bfq_idle_slice_timer(unsigned long data)
{
struct bfq_data *bfqd = (struct bfq_data *)data;
struct bfq_queue *bfqq;
unsigned long flags;
enum bfqq_expiration reason;
spin_lock_irqsave(bfqd->queue->queue_lock, flags);
bfqq = bfqd->in_service_queue;
/*
* Theoretical race here: the in-service queue can be NULL or
* different from the queue that was idling if the timer handler
* spins on the queue_lock and a new request arrives for the
* current queue and there is a full dispatch cycle that changes
* the in-service queue. This can hardly happen, but in the worst
* case we just expire a queue too early.
*/
if (bfqq != NULL) {
bfq_log_bfqq(bfqd, bfqq, "slice_timer expired");
if (bfq_bfqq_budget_timeout(bfqq))
/*
* Also here the queue can be safely expired
* for budget timeout without wasting
* guarantees
*/
reason = BFQ_BFQQ_BUDGET_TIMEOUT;
else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0)
/*
* The queue may not be empty upon timer expiration,
* because we may not disable the timer when the
* first request of the in-service queue arrives
* during disk idling.
*/
reason = BFQ_BFQQ_TOO_IDLE;
else
goto schedule_dispatch;
bfq_bfqq_expire(bfqd, bfqq, 1, reason);
}
schedule_dispatch:
bfq_schedule_dispatch(bfqd);
spin_unlock_irqrestore(bfqd->queue->queue_lock, flags);
}
static void bfq_shutdown_timer_wq(struct bfq_data *bfqd)
{
del_timer_sync(&bfqd->idle_slice_timer);
cancel_work_sync(&bfqd->unplug_work);
}
static inline void __bfq_put_async_bfqq(struct bfq_data *bfqd,
struct bfq_queue **bfqq_ptr)
{
struct bfq_group *root_group = bfqd->root_group;
struct bfq_queue *bfqq = *bfqq_ptr;
bfq_log(bfqd, "put_async_bfqq: %p", bfqq);
if (bfqq != NULL) {
bfq_bfqq_move(bfqd, bfqq, &bfqq->entity, root_group);
bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d",
bfqq, atomic_read(&bfqq->ref));
bfq_put_queue(bfqq);
*bfqq_ptr = NULL;
}
}
/*
* Release all the bfqg references to its async queues. If we are
* deallocating the group these queues may still contain requests, so
* we reparent them to the root cgroup (i.e., the only one that will
* exist for sure until all the requests on a device are gone).
*/
static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
{
int i, j;
for (i = 0; i < 2; i++)
for (j = 0; j < IOPRIO_BE_NR; j++)
__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
}
static void bfq_exit_queue(struct elevator_queue *e)
{
struct bfq_data *bfqd = e->elevator_data;
struct request_queue *q = bfqd->queue;
struct bfq_queue *bfqq, *n;
bfq_shutdown_timer_wq(bfqd);
spin_lock_irq(q->queue_lock);
BUG_ON(bfqd->in_service_queue != NULL);
list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
bfq_deactivate_bfqq(bfqd, bfqq, 0);
bfq_disconnect_groups(bfqd);
spin_unlock_irq(q->queue_lock);
bfq_shutdown_timer_wq(bfqd);
synchronize_rcu();
BUG_ON(timer_pending(&bfqd->idle_slice_timer));
bfq_free_root_group(bfqd);
kfree(bfqd);
}
static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
{
struct bfq_group *bfqg;
struct bfq_data *bfqd;
struct elevator_queue *eq;
eq = elevator_alloc(q, e);
if (eq == NULL)
return -ENOMEM;
bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
if (bfqd == NULL) {
kobject_put(&eq->kobj);
return -ENOMEM;
}
eq->elevator_data = bfqd;
/*
* Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues.
* Grab a permanent reference to it, so that the normal code flow
* will not attempt to free it.
*/
bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0);
atomic_inc(&bfqd->oom_bfqq.ref);
bfqd->oom_bfqq.entity.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO;
bfqd->oom_bfqq.entity.new_ioprio_class = IOPRIO_CLASS_BE;
bfqd->oom_bfqq.entity.new_weight =
bfq_ioprio_to_weight(bfqd->oom_bfqq.entity.new_ioprio);
/*
* Trigger weight initialization, according to ioprio, at the
* oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio
* class won't be changed any more.
*/
bfqd->oom_bfqq.entity.ioprio_changed = 1;
bfqd->queue = q;
spin_lock_irq(q->queue_lock);
q->elevator = eq;
spin_unlock_irq(q->queue_lock);
bfqg = bfq_alloc_root_group(bfqd, q->node);
if (bfqg == NULL) {
kfree(bfqd);
kobject_put(&eq->kobj);
return -ENOMEM;
}
bfqd->root_group = bfqg;
bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group);
#ifdef CONFIG_CGROUP_BFQIO
bfqd->active_numerous_groups = 0;
#endif
init_timer(&bfqd->idle_slice_timer);
bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
bfqd->idle_slice_timer.data = (unsigned long)bfqd;
bfqd->rq_pos_tree = RB_ROOT;
bfqd->queue_weights_tree = RB_ROOT;
bfqd->group_weights_tree = RB_ROOT;
INIT_WORK(&bfqd->unplug_work, bfq_kick_queue);
INIT_LIST_HEAD(&bfqd->active_list);
INIT_LIST_HEAD(&bfqd->idle_list);
INIT_HLIST_HEAD(&bfqd->burst_list);
bfqd->hw_tag = -1;
bfqd->bfq_max_budget = bfq_default_max_budget;
bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0];
bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1];
bfqd->bfq_back_max = bfq_back_max;
bfqd->bfq_back_penalty = bfq_back_penalty;
bfqd->bfq_slice_idle = bfq_slice_idle;
bfqd->bfq_class_idle_last_service = 0;
bfqd->bfq_max_budget_async_rq = bfq_max_budget_async_rq;
bfqd->bfq_timeout[BLK_RW_ASYNC] = bfq_timeout_async;
bfqd->bfq_timeout[BLK_RW_SYNC] = bfq_timeout_sync;
bfqd->bfq_coop_thresh = 2;
bfqd->bfq_failed_cooperations = 7000;
bfqd->bfq_requests_within_timer = 120;
bfqd->bfq_large_burst_thresh = 11;
bfqd->bfq_burst_interval = msecs_to_jiffies(500);
bfqd->low_latency = true;
bfqd->bfq_wr_coeff = 20;
bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300);
bfqd->bfq_wr_max_time = 0;
bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000);
bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500);
bfqd->bfq_wr_max_softrt_rate = 7000; /*
* Approximate rate required
* to playback or record a
* high-definition compressed
* video.
*/
bfqd->wr_busy_queues = 0;
bfqd->busy_in_flight_queues = 0;
bfqd->const_seeky_busy_in_flight_queues = 0;
/*
* Begin by assuming, optimistically, that the device peak rate is
* equal to the highest reference rate.
*/
bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] *
T_fast[blk_queue_nonrot(bfqd->queue)];
bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)];
bfqd->device_speed = BFQ_BFQD_FAST;
return 0;
}
static void bfq_slab_kill(void)
{
if (bfq_pool != NULL)
kmem_cache_destroy(bfq_pool);
}
static int __init bfq_slab_setup(void)
{
bfq_pool = KMEM_CACHE(bfq_queue, 0);
if (bfq_pool == NULL)
return -ENOMEM;
return 0;
}
static ssize_t bfq_var_show(unsigned int var, char *page)
{
return sprintf(page, "%d\n", var);
}
static ssize_t bfq_var_store(unsigned long *var, const char *page,
size_t count)
{
unsigned long new_val;
int ret = kstrtoul(page, 10, &new_val);
if (ret == 0)
*var = new_val;
return count;
}
static ssize_t bfq_wr_max_time_show(struct elevator_queue *e, char *page)
{
struct bfq_data *bfqd = e->elevator_data;
return sprintf(page, "%d\n", bfqd->bfq_wr_max_time > 0 ?
jiffies_to_msecs(bfqd->bfq_wr_max_time) :
jiffies_to_msecs(bfq_wr_duration(bfqd)));
}
static ssize_t bfq_weights_show(struct elevator_queue *e, char *page)
{
struct bfq_queue *bfqq;
struct bfq_data *bfqd = e->elevator_data;
ssize_t num_char = 0;
num_char += sprintf(page + num_char, "Tot reqs queued %d\n\n",
bfqd->queued);
spin_lock_irq(bfqd->queue->queue_lock);
num_char += sprintf(page + num_char, "Active:\n");
list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) {
num_char += sprintf(page + num_char,
"pid%d: weight %hu, nr_queued %d %d, dur %d/%u\n",
bfqq->pid,
bfqq->entity.weight,
bfqq->queued[0],
bfqq->queued[1],
jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
jiffies_to_msecs(bfqq->wr_cur_max_time));
}
num_char += sprintf(page + num_char, "Idle:\n");
list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) {
num_char += sprintf(page + num_char,
"pid%d: weight %hu, dur %d/%u\n",
bfqq->pid,
bfqq->entity.weight,
jiffies_to_msecs(jiffies -
bfqq->last_wr_start_finish),
jiffies_to_msecs(bfqq->wr_cur_max_time));
}
spin_unlock_irq(bfqd->queue->queue_lock);
return num_char;
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
{ \
struct bfq_data *bfqd = e->elevator_data; \
unsigned int __data = __VAR; \
if (__CONV) \
__data = jiffies_to_msecs(__data); \
return bfq_var_show(__data, (page)); \
}
SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 1);
SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 1);
SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0);
SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0);
SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 1);
SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0);
SHOW_FUNCTION(bfq_max_budget_async_rq_show,
bfqd->bfq_max_budget_async_rq, 0);
SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout[BLK_RW_SYNC], 1);
SHOW_FUNCTION(bfq_timeout_async_show, bfqd->bfq_timeout[BLK_RW_ASYNC], 1);
SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0);
SHOW_FUNCTION(bfq_wr_coeff_show, bfqd->bfq_wr_coeff, 0);
SHOW_FUNCTION(bfq_wr_rt_max_time_show, bfqd->bfq_wr_rt_max_time, 1);
SHOW_FUNCTION(bfq_wr_min_idle_time_show, bfqd->bfq_wr_min_idle_time, 1);
SHOW_FUNCTION(bfq_wr_min_inter_arr_async_show, bfqd->bfq_wr_min_inter_arr_async,
1);
SHOW_FUNCTION(bfq_wr_max_softrt_rate_show, bfqd->bfq_wr_max_softrt_rate, 0);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t \
__FUNC(struct elevator_queue *e, const char *page, size_t count) \
{ \
struct bfq_data *bfqd = e->elevator_data; \
unsigned long uninitialized_var(__data); \
int ret = bfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
if (__CONV) \
*(__PTR) = msecs_to_jiffies(__data); \
else \
*(__PTR) = __data; \
return ret; \
}
STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1,
INT_MAX, 1);
STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1,
INT_MAX, 1);
STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0);
STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1,
INT_MAX, 0);
STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 1);
STORE_FUNCTION(bfq_max_budget_async_rq_store, &bfqd->bfq_max_budget_async_rq,
1, INT_MAX, 0);
STORE_FUNCTION(bfq_timeout_async_store, &bfqd->bfq_timeout[BLK_RW_ASYNC], 0,
INT_MAX, 1);
STORE_FUNCTION(bfq_wr_coeff_store, &bfqd->bfq_wr_coeff, 1, INT_MAX, 0);
STORE_FUNCTION(bfq_wr_max_time_store, &bfqd->bfq_wr_max_time, 0, INT_MAX, 1);
STORE_FUNCTION(bfq_wr_rt_max_time_store, &bfqd->bfq_wr_rt_max_time, 0, INT_MAX,
1);
STORE_FUNCTION(bfq_wr_min_idle_time_store, &bfqd->bfq_wr_min_idle_time, 0,
INT_MAX, 1);
STORE_FUNCTION(bfq_wr_min_inter_arr_async_store,
&bfqd->bfq_wr_min_inter_arr_async, 0, INT_MAX, 1);
STORE_FUNCTION(bfq_wr_max_softrt_rate_store, &bfqd->bfq_wr_max_softrt_rate, 0,
INT_MAX, 0);
#undef STORE_FUNCTION
/* do nothing for the moment */
static ssize_t bfq_weights_store(struct elevator_queue *e,
const char *page, size_t count)
{
return count;
}
static inline unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd)
{
u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES)
return bfq_calc_max_budget(bfqd->peak_rate, timeout);
else
return bfq_default_max_budget;
}
static ssize_t bfq_max_budget_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data == 0)
bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
else {
if (__data > INT_MAX)
__data = INT_MAX;
bfqd->bfq_max_budget = __data;
}
bfqd->bfq_user_max_budget = __data;
return ret;
}
static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data < 1)
__data = 1;
else if (__data > INT_MAX)
__data = INT_MAX;
bfqd->bfq_timeout[BLK_RW_SYNC] = msecs_to_jiffies(__data);
if (bfqd->bfq_user_max_budget == 0)
bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
return ret;
}
static ssize_t bfq_low_latency_store(struct elevator_queue *e,
const char *page, size_t count)
{
struct bfq_data *bfqd = e->elevator_data;
unsigned long uninitialized_var(__data);
int ret = bfq_var_store(&__data, (page), count);
if (__data > 1)
__data = 1;
if (__data == 0 && bfqd->low_latency != 0)
bfq_end_wr(bfqd);
bfqd->low_latency = __data;
return ret;
}
#define BFQ_ATTR(name) \
__ATTR(name, S_IRUGO|S_IWUSR, bfq_##name##_show, bfq_##name##_store)
static struct elv_fs_entry bfq_attrs[] = {
BFQ_ATTR(fifo_expire_sync),
BFQ_ATTR(fifo_expire_async),
BFQ_ATTR(back_seek_max),
BFQ_ATTR(back_seek_penalty),
BFQ_ATTR(slice_idle),
BFQ_ATTR(max_budget),
BFQ_ATTR(max_budget_async_rq),
BFQ_ATTR(timeout_sync),
BFQ_ATTR(timeout_async),
BFQ_ATTR(low_latency),
BFQ_ATTR(wr_coeff),
BFQ_ATTR(wr_max_time),
BFQ_ATTR(wr_rt_max_time),
BFQ_ATTR(wr_min_idle_time),
BFQ_ATTR(wr_min_inter_arr_async),
BFQ_ATTR(wr_max_softrt_rate),
BFQ_ATTR(weights),
__ATTR_NULL
};
static struct elevator_type iosched_bfq = {
.ops = {
.elevator_merge_fn = bfq_merge,
.elevator_merged_fn = bfq_merged_request,
.elevator_merge_req_fn = bfq_merged_requests,
.elevator_allow_merge_fn = bfq_allow_merge,
.elevator_dispatch_fn = bfq_dispatch_requests,
.elevator_add_req_fn = bfq_insert_request,
.elevator_activate_req_fn = bfq_activate_request,
.elevator_deactivate_req_fn = bfq_deactivate_request,
.elevator_completed_req_fn = bfq_completed_request,
.elevator_former_req_fn = elv_rb_former_request,
.elevator_latter_req_fn = elv_rb_latter_request,
.elevator_init_icq_fn = bfq_init_icq,
.elevator_exit_icq_fn = bfq_exit_icq,
.elevator_set_req_fn = bfq_set_request,
.elevator_put_req_fn = bfq_put_request,
.elevator_may_queue_fn = bfq_may_queue,
.elevator_init_fn = bfq_init_queue,
.elevator_exit_fn = bfq_exit_queue,
},
.icq_size = sizeof(struct bfq_io_cq),
.icq_align = __alignof__(struct bfq_io_cq),
.elevator_attrs = bfq_attrs,
.elevator_name = "bfq",
.elevator_owner = THIS_MODULE,
};
static int __init bfq_init(void)
{
/*
* Can be 0 on HZ < 1000 setups.
*/
if (bfq_slice_idle == 0)
bfq_slice_idle = 1;
if (bfq_timeout_async == 0)
bfq_timeout_async = 1;
if (bfq_slab_setup())
return -ENOMEM;
/*
* Times to load large popular applications for the typical systems
* installed on the reference devices (see the comments before the
* definitions of the two arrays).
*/
T_slow[0] = msecs_to_jiffies(2600);
T_slow[1] = msecs_to_jiffies(1000);
T_fast[0] = msecs_to_jiffies(5500);
T_fast[1] = msecs_to_jiffies(2000);
/*
* Thresholds that determine the switch between speed classes (see
* the comments before the definition of the array).
*/
device_speed_thresh[0] = (R_fast[0] + R_slow[0]) / 2;
device_speed_thresh[1] = (R_fast[1] + R_slow[1]) / 2;
elv_register(&iosched_bfq);
pr_info("BFQ I/O-scheduler: v7r8");
return 0;
}
static void __exit bfq_exit(void)
{
elv_unregister(&iosched_bfq);
bfq_slab_kill();
}
module_init(bfq_init);
module_exit(bfq_exit);
MODULE_AUTHOR("Fabio Checconi, Paolo Valente");
MODULE_LICENSE("GPL");
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