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authorJens Axboe <jens.axboe@oracle.com>2007-01-18 19:56:49 -0500
committerJens Axboe <axboe@carl.home.kernel.dk>2007-02-11 17:14:45 -0500
commitc5b680f3b7593f2b066c683df799d19f807fb23d (patch)
tree657df453cdf7b872f5ea713e66f2e090048a6c1f /block/cfq-iosched.c
parent44f7c16065c83060cbb9dd9b367141682a6e2b8e (diff)
cfq-iosched: account for slice over/under time
If a slice uses less than it is entitled to (or perhaps more), include that in the decision on how much time to give it the next time it gets serviced. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c32
1 files changed, 12 insertions, 20 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d44402a4c5cd..039b38cf805c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -147,8 +147,8 @@ struct cfq_queue {
147 struct list_head fifo; 147 struct list_head fifo;
148 148
149 unsigned long slice_end; 149 unsigned long slice_end;
150 unsigned long slice_left;
151 unsigned long service_last; 150 unsigned long service_last;
151 long slice_resid;
152 152
153 /* number of requests that are on the dispatch list */ 153 /* number of requests that are on the dispatch list */
154 int on_dispatch[2]; 154 int on_dispatch[2];
@@ -251,6 +251,14 @@ static inline void
251cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq) 251cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
252{ 252{
253 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies; 253 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
254 cfqq->slice_end += cfqq->slice_resid;
255
256 /*
257 * Don't carry over residual for more than one slice, we only want
258 * to slightly correct the fairness. Carrying over forever would
259 * easily introduce oscillations.
260 */
261 cfqq->slice_resid = 0;
254} 262}
255 263
256/* 264/*
@@ -667,7 +675,6 @@ __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
667 del_timer(&cfqd->idle_class_timer); 675 del_timer(&cfqd->idle_class_timer);
668 676
669 cfqq->slice_end = 0; 677 cfqq->slice_end = 0;
670 cfqq->slice_left = 0;
671 cfq_clear_cfqq_must_alloc_slice(cfqq); 678 cfq_clear_cfqq_must_alloc_slice(cfqq);
672 cfq_clear_cfqq_fifo_expire(cfqq); 679 cfq_clear_cfqq_fifo_expire(cfqq);
673 cfq_mark_cfqq_slice_new(cfqq); 680 cfq_mark_cfqq_slice_new(cfqq);
@@ -683,8 +690,6 @@ static void
683__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq, 690__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
684 int preempted) 691 int preempted)
685{ 692{
686 unsigned long now = jiffies;
687
688 if (cfq_cfqq_wait_request(cfqq)) 693 if (cfq_cfqq_wait_request(cfqq))
689 del_timer(&cfqd->idle_slice_timer); 694 del_timer(&cfqd->idle_slice_timer);
690 695
@@ -699,10 +704,8 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
699 * store what was left of this slice, if the queue idled out 704 * store what was left of this slice, if the queue idled out
700 * or was preempted 705 * or was preempted
701 */ 706 */
702 if (cfq_slice_used(cfqq)) 707 if (!cfq_cfqq_slice_new(cfqq))
703 cfqq->slice_left = cfqq->slice_end - now; 708 cfqq->slice_resid = cfqq->slice_end - jiffies;
704 else
705 cfqq->slice_left = 0;
706 709
707 cfq_resort_rr_list(cfqq, preempted); 710 cfq_resort_rr_list(cfqq, preempted);
708 711
@@ -1364,10 +1367,7 @@ retry:
1364 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]); 1367 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1365 atomic_set(&cfqq->ref, 0); 1368 atomic_set(&cfqq->ref, 0);
1366 cfqq->cfqd = cfqd; 1369 cfqq->cfqd = cfqd;
1367 /* 1370
1368 * set ->slice_left to allow preemption for a new process
1369 */
1370 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1371 cfq_mark_cfqq_idle_window(cfqq); 1371 cfq_mark_cfqq_idle_window(cfqq);
1372 cfq_mark_cfqq_prio_changed(cfqq); 1372 cfq_mark_cfqq_prio_changed(cfqq);
1373 cfq_mark_cfqq_queue_new(cfqq); 1373 cfq_mark_cfqq_queue_new(cfqq);
@@ -1586,11 +1586,6 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1586 if (!cfq_cfqq_wait_request(new_cfqq)) 1586 if (!cfq_cfqq_wait_request(new_cfqq))
1587 return 0; 1587 return 0;
1588 /* 1588 /*
1589 * if it doesn't have slice left, forget it
1590 */
1591 if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1592 return 0;
1593 /*
1594 * if the new request is sync, but the currently running queue is 1589 * if the new request is sync, but the currently running queue is
1595 * not, let the sync request have priority. 1590 * not, let the sync request have priority.
1596 */ 1591 */
@@ -1614,9 +1609,6 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1614{ 1609{
1615 cfq_slice_expired(cfqd, 1); 1610 cfq_slice_expired(cfqd, 1);
1616 1611
1617 if (!cfqq->slice_left)
1618 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1619
1620 /* 1612 /*
1621 * Put the new queue at the front of the of the current list, 1613 * Put the new queue at the front of the of the current list,
1622 * so we know that it will be selected next. 1614 * so we know that it will be selected next.