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[PATCH] cfq-iosched.c: minor fixes 

One critical fix and two minor fixes for 2.6.13-rc7:

- Max depth must currently be 2 to allow barriers to function on SCSI
- Prefer sync request over async in choosing the next request
- Never allow async request to preempt or disturb the "anticipation" for
  a single cfq process context. This is as-designed, the code right now
  is buggy in that area.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jens Axboe 2005-08-24 14:57:54 +02:00 committed by Linus Torvalds
parent 41290c1464
commit 9c2c38a122
1 changed files with 21 additions and 10 deletions
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31
drivers/block/cfq-iosched.c
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@ -47,7 +47,7 @@ static int cfq_slice_idle = HZ / 100;
/* /*
* disable queueing at the driver/hardware level * disable queueing at the driver/hardware level
*/ */
static int cfq_max_depth = 1; static int cfq_max_depth = 2;
/* /*
* for the hash of cfqq inside the cfqd * for the hash of cfqq inside the cfqd
@ -385,9 +385,15 @@ cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
return crq2; return crq2;
if (crq2 == NULL) if (crq2 == NULL)
return crq1; return crq1;
if (cfq_crq_requeued(crq1))
if (cfq_crq_requeued(crq1) && !cfq_crq_requeued(crq2))
return crq1; return crq1;
if (cfq_crq_requeued(crq2)) else if (cfq_crq_requeued(crq2) && !cfq_crq_requeued(crq1))
return crq2;
if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
return crq1;
else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
return crq2; return crq2;
s1 = crq1->request->sector; s1 = crq1->request->sector;
@ -1769,18 +1775,23 @@ static void
cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_rq *crq) struct cfq_rq *crq)
{ {
const int sync = cfq_crq_is_sync(crq); struct cfq_io_context *cic;
cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq); cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
if (sync) { /*
struct cfq_io_context *cic = crq->io_context; * we never wait for an async request and we don't allow preemption
* of an async request. so just return early
*/
if (!cfq_crq_is_sync(crq))
return;
cfq_update_io_thinktime(cfqd, cic); cic = crq->io_context;
cfq_update_idle_window(cfqd, cfqq, cic);
cic->last_queue = jiffies; cfq_update_io_thinktime(cfqd, cic);
} cfq_update_idle_window(cfqd, cfqq, cic);
cic->last_queue = jiffies;
if (cfqq == cfqd->active_queue) { if (cfqq == cfqd->active_queue) {
/* /*