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raid5: make_request use batch stripe release

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make_request() does stripe release for every stripe and the stripe usually has
count 1, which makes previous release_stripe() optimization not work. In my
test, this release_stripe() becomes the heaviest pleace to take
conf->device_lock after previous patches applied.

Below patch makes stripe release batch. All the stripes will be released in
unplug. The STRIPE_ON_UNPLUG_LIST bit is to protect concurrent access stripe
lru.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
Shaohua Li 2012-08-02 08:33:00 +10:00 committed by NeilBrown
parent 74018dc306
commit 8811b5968f
2 changed files with 60 additions and 3 deletions
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62
drivers/md/raid5.c
View file

@ -471,7 +471,8 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
} else {
if (atomic_read(&sh->count)) {
BUG_ON(!list_empty(&sh->lru)
&& !test_bit(STRIPE_EXPANDING, &sh->state));
&& !test_bit(STRIPE_EXPANDING, &sh->state)
&& !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state));
} else {
if (!test_bit(STRIPE_HANDLE, &sh->state))
atomic_inc(&conf->active_stripes);
@ -3988,6 +3989,62 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf)
return sh;
}
struct raid5_plug_cb {
struct blk_plug_cb cb;
struct list_head list;
};
static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
{
struct raid5_plug_cb *cb = container_of(
blk_cb, struct raid5_plug_cb, cb);
struct stripe_head *sh;
struct mddev *mddev = cb->cb.data;
struct r5conf *conf = mddev->private;
if (cb->list.next && !list_empty(&cb->list)) {
spin_lock_irq(&conf->device_lock);
while (!list_empty(&cb->list)) {
sh = list_first_entry(&cb->list, struct stripe_head, lru);
list_del_init(&sh->lru);
/*
* avoid race release_stripe_plug() sees
* STRIPE_ON_UNPLUG_LIST clear but the stripe
* is still in our list
*/
smp_mb__before_clear_bit();
clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);
__release_stripe(conf, sh);
}
spin_unlock_irq(&conf->device_lock);
}
kfree(cb);
}
static void release_stripe_plug(struct mddev *mddev,
struct stripe_head *sh)
{
struct blk_plug_cb *blk_cb = blk_check_plugged(
raid5_unplug, mddev,
sizeof(struct raid5_plug_cb));
struct raid5_plug_cb *cb;
if (!blk_cb) {
release_stripe(sh);
return;
}
cb = container_of(blk_cb, struct raid5_plug_cb, cb);
if (cb->list.next == NULL)
INIT_LIST_HEAD(&cb->list);
if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))
list_add_tail(&sh->lru, &cb->list);
else
release_stripe(sh);
}
static void make_request(struct mddev *mddev, struct bio * bi)
{
struct r5conf *conf = mddev->private;
@ -4116,8 +4173,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
if ((bi->bi_rw & REQ_SYNC) &&
!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
atomic_inc(&conf->preread_active_stripes);
mddev_check_plugged(mddev);
release_stripe(sh);
release_stripe_plug(mddev, sh);
} else {
/* cannot get stripe for read-ahead, just give-up */
clear_bit(BIO_UPTODATE, &bi->bi_flags);

1
drivers/md/raid5.h
View file

@ -319,6 +319,7 @@ enum {
STRIPE_BIOFILL_RUN,
STRIPE_COMPUTE_RUN,
STRIPE_OPS_REQ_PENDING,
STRIPE_ON_UNPLUG_LIST,
};
/*