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authorJens Axboe <jens.axboe@oracle.com>2007-02-14 13:59:49 -0500
committerJens Axboe <axboe@nelson.home.kernel.dk>2007-04-30 03:01:21 -0400
commit1e3335de05da3dfbe48b8caa03db1834a2133256 (patch)
tree3783ea1ef788f564a78754906dc508ac66595b75 /block/cfq-iosched.c
parentb9099ff63c75216d6ca10bce5a1abcd9293c27e6 (diff)
cfq-iosched: improve preemption for cooperating tasks
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>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c26
1 files changed, 20 insertions, 6 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f92ba2a869b4..bfb396774cbb 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -867,15 +867,11 @@ static int cfq_arm_slice_timer(struct cfq_data *cfqd)
867 867
868static void cfq_dispatch_insert(request_queue_t *q, struct request *rq) 868static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
869{ 869{
870 struct cfq_data *cfqd = q->elevator->elevator_data;
871 struct cfq_queue *cfqq = RQ_CFQQ(rq); 870 struct cfq_queue *cfqq = RQ_CFQQ(rq);
872 871
873 cfq_remove_request(rq); 872 cfq_remove_request(rq);
874 cfqq->on_dispatch[rq_is_sync(rq)]++; 873 cfqq->on_dispatch[rq_is_sync(rq)]++;
875 elv_dispatch_sort(q, rq); 874 elv_dispatch_sort(q, rq);
876
877 rq = list_entry(q->queue_head.prev, struct request, queuelist);
878 cfqd->last_sector = rq->sector + rq->nr_sectors;
879} 875}
880 876
881/* 877/*
@@ -1585,6 +1581,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1585 struct request *rq) 1581 struct request *rq)
1586{ 1582{
1587 struct cfq_queue *cfqq = cfqd->active_queue; 1583 struct cfq_queue *cfqq = cfqd->active_queue;
1584 sector_t dist;
1588 1585
1589 if (cfq_class_idle(new_cfqq)) 1586 if (cfq_class_idle(new_cfqq))
1590 return 0; 1587 return 0;
@@ -1594,14 +1591,14 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1594 1591
1595 if (cfq_class_idle(cfqq)) 1592 if (cfq_class_idle(cfqq))
1596 return 1; 1593 return 1;
1597 if (!cfq_cfqq_wait_request(new_cfqq)) 1594
1598 return 0;
1599 /* 1595 /*
1600 * if the new request is sync, but the currently running queue is 1596 * if the new request is sync, but the currently running queue is
1601 * not, let the sync request have priority. 1597 * not, let the sync request have priority.
1602 */ 1598 */
1603 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) 1599 if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1604 return 1; 1600 return 1;
1601
1605 /* 1602 /*
1606 * So both queues are sync. Let the new request get disk time if 1603 * So both queues are sync. Let the new request get disk time if
1607 * it's a metadata request and the current queue is doing regular IO. 1604 * it's a metadata request and the current queue is doing regular IO.
@@ -1609,6 +1606,21 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1609 if (rq_is_meta(rq) && !cfqq->meta_pending) 1606 if (rq_is_meta(rq) && !cfqq->meta_pending)
1610 return 1; 1607 return 1;
1611 1608
1609 if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1610 return 0;
1611
1612 /*
1613 * if this request is as-good as one we would expect from the
1614 * current cfqq, let it preempt
1615 */
1616 if (rq->sector > cfqd->last_sector)
1617 dist = rq->sector - cfqd->last_sector;
1618 else
1619 dist = cfqd->last_sector - rq->sector;
1620
1621 if (dist <= cfqd->active_cic->seek_mean)
1622 return 1;
1623
1612 return 0; 1624 return 0;
1613} 1625}
1614 1626
@@ -1719,6 +1731,8 @@ static void cfq_completed_request(request_queue_t *q, struct request *rq)
1719 cfqq->on_dispatch[sync]--; 1731 cfqq->on_dispatch[sync]--;
1720 cfqq->service_last = now; 1732 cfqq->service_last = now;
1721 1733
1734 cfqd->last_sector = rq->hard_sector + rq->hard_nr_sectors;
1735
1722 if (!cfq_class_idle(cfqq)) 1736 if (!cfq_class_idle(cfqq))
1723 cfqd->last_end_request = now; 1737 cfqd->last_end_request = now;
1724 1738