Messages in this thread Patch in this message | | | From | Jens Axboe <> | Subject | [PATCH 1/15] cfq-iosched: improve preemption for cooperating tasks | Date | Tue, 24 Apr 2007 10:15:29 +0200 |
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When testing the syslet async io approach, I discovered that CFQ sometimes didn't perform as well as expected. cfq_should_preempt() needs to better check for cooperating tasks, so fix that by allowing preemption of an equal priority queue if the recently queued request is as good a candidate for IO as the one we are currently waiting for.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com> --- block/cfq-iosched.c | 26 ++++++++++++++++++++------ 1 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 9e37971..a683d00 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -861,15 +861,11 @@ static int cfq_arm_slice_timer(struct cfq_data *cfqd) static void cfq_dispatch_insert(request_queue_t *q, struct request *rq) { - struct cfq_data *cfqd = q->elevator->elevator_data; struct cfq_queue *cfqq = RQ_CFQQ(rq); cfq_remove_request(rq); cfqq->on_dispatch[rq_is_sync(rq)]++; elv_dispatch_sort(q, rq); - - rq = list_entry(q->queue_head.prev, struct request, queuelist); - cfqd->last_sector = rq->sector + rq->nr_sectors; } /* @@ -1579,6 +1575,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, struct request *rq) { struct cfq_queue *cfqq = cfqd->active_queue; + sector_t dist; if (cfq_class_idle(new_cfqq)) return 0; @@ -1588,14 +1585,14 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if (cfq_class_idle(cfqq)) return 1; - if (!cfq_cfqq_wait_request(new_cfqq)) - return 0; + /* * if the new request is sync, but the currently running queue is * not, let the sync request have priority. */ if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) return 1; + /* * So both queues are sync. Let the new request get disk time if * it's a metadata request and the current queue is doing regular IO. @@ -1603,6 +1600,21 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, if (rq_is_meta(rq) && !cfqq->meta_pending) return 1; + if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq)) + return 0; + + /* + * if this request is as-good as one we would expect from the + * current cfqq, let it preempt + */ + if (rq->sector > cfqd->last_sector) + dist = rq->sector - cfqd->last_sector; + else + dist = cfqd->last_sector - rq->sector; + + if (dist <= cfqd->active_cic->seek_mean) + return 1; + return 0; } @@ -1719,6 +1731,8 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq) cfqq->on_dispatch[sync]--; cfqq->service_last = now; + cfqd->last_sector = rq->hard_sector + rq->hard_nr_sectors; + if (!cfq_class_idle(cfqq)) cfqd->last_end_request = now; -- 1.5.1.1.190.g74474 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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