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cfq-iosched: drain device queue before switching to a sync queue

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To lessen the impact of async IO on sync IO, let the device drain of
any async IO in progress when switching to a sync cfqq that has idling
enabled.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2009-07-03 12:57:48 +02:00
parent da6c5c720c
commit 5ad531db6e
1 changed files with 25 additions and 13 deletions
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38
block/cfq-iosched.c
View file

@ -140,7 +140,7 @@ struct cfq_data {
*/
unsigned int busy_rt_queues;
int rq_in_driver;
int rq_in_driver[2];
int sync_flight;
/*
@ -239,6 +239,11 @@ static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
struct io_context *);
static inline int rq_in_driver(struct cfq_data *cfqd)
{
return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
}
static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
int is_sync)
{
@ -760,9 +765,9 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
cfqd->rq_in_driver++;
cfqd->rq_in_driver[rq_is_sync(rq)]++;
cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
cfqd->rq_in_driver);
rq_in_driver(cfqd));
cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
}
@ -770,11 +775,12 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
const int sync = rq_is_sync(rq);
WARN_ON(!cfqd->rq_in_driver);
cfqd->rq_in_driver--;
WARN_ON(!cfqd->rq_in_driver[sync]);
cfqd->rq_in_driver[sync]--;
cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
cfqd->rq_in_driver);
rq_in_driver(cfqd));
}
static void cfq_remove_request(struct request *rq)
@ -1080,7 +1086,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
/*
* still requests with the driver, don't idle
*/
if (cfqd->rq_in_driver)
if (rq_in_driver(cfqd))
return;
/*
@ -1311,6 +1317,12 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
if (!cfqq)
return 0;
/*
* Drain async requests before we start sync IO
*/
if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
return 0;
/*
* If this is an async queue and we have sync IO in flight, let it wait
*/
@ -2130,11 +2142,11 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
*/
static void cfq_update_hw_tag(struct cfq_data *cfqd)
{
if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak)
cfqd->rq_in_driver_peak = cfqd->rq_in_driver;
if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
return;
if (cfqd->hw_tag_samples++ < 50)
@ -2161,9 +2173,9 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
cfq_update_hw_tag(cfqd);
WARN_ON(!cfqd->rq_in_driver);
WARN_ON(!cfqd->rq_in_driver[sync]);
WARN_ON(!cfqq->dispatched);
cfqd->rq_in_driver--;
cfqd->rq_in_driver[sync]--;
cfqq->dispatched--;
if (cfq_cfqq_sync(cfqq))
@ -2197,7 +2209,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
cfq_arm_slice_timer(cfqd);
}
if (!cfqd->rq_in_driver)
if (!rq_in_driver(cfqd))
cfq_schedule_dispatch(cfqd);
}