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block: row-iosched idling triggered by readahead pages 

In the current implementation idling is triggered only by request
insertion frequency. This heuristic is not very accurate and may hit
random requests that shouldn't trigger idling. This patch uses the
PG_readahead flag in struct page's flags, which indicates that the page
is part of a readahead window, to start idling upon dispatch of a request
associated with a readahead page.

The above readehead flag is used together with the existing
insertion-frequency trigger. The frequency timer will catch read requests
which are not part of a readahead window, but are still part of a
sequential stream (and therefore dispatched in small time intervals).

Change-Id: Icb7145199c007408de3f267645ccb842e051fd00
Signed-off-by: Lee Susman <lsusman@codeaurora.org>
This commit is contained in:
Lee Susman 2013-06-23 16:27:40 +03:00 committed by Stephen Boyd
parent a4fe692df6
commit 80a8f0f87b
1 changed files with 8 additions and 2 deletions
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10
block/row-iosched.c
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@ -97,7 +97,7 @@ static const struct row_queue_params row_queues_def[] = {
/* Default values for idling on read queues (in msec) */
#define ROW_IDLE_TIME_MSEC 5
#define ROW_READ_FREQ_MSEC 20
#define ROW_READ_FREQ_MSEC 5
/**
* struct rowq_idling_data - parameters for idling on the queue
@ -331,6 +331,10 @@ static void row_add_request(struct request_queue *q,
struct row_queue *rqueue = RQ_ROWQ(rq);
s64 diff_ms;
bool queue_was_empty = list_empty(&rqueue->fifo);
unsigned long bv_page_flags = 0;
if (rq->bio && rq->bio->bi_io_vec && rq->bio->bi_io_vec->bv_page)
bv_page_flags = rq->bio->bi_io_vec->bv_page->flags;
list_add_tail(&rq->queuelist, &rqueue->fifo);
rd->nr_reqs[rq_data_dir(rq)]++;
@ -360,7 +364,9 @@ static void row_add_request(struct request_queue *q,
rqueue->idle_data.begin_idling = false;
return;
}
if (diff_ms < rd->rd_idle_data.freq_ms) {
if ((bv_page_flags & (1L << PG_readahead)) ||
(diff_ms < rd->rd_idle_data.freq_ms)) {
rqueue->idle_data.begin_idling = true;
row_log_rowq(rd, rqueue->prio, "Enable idling");
} else {