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authorCorrado Zoccolo <czoccolo@gmail.com>2009-10-08 08:43:32 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-10-08 08:43:32 +0200
commit355b659c87432a4e76160640625c47fcf9174e8d (patch)
tree1121f7c4ae13643a30abaf6091312f5b116a52bc /block
parenta6151c3a5c8e1ff5a28450bc8d6a99a2a0add0a7 (diff)
cfq-iosched: avoid probable slice overrun when idling
If the average think time is larger than the remaining time slice for any given queue, don't allow it to idle. A succesful idle also means that we need to dispatch and complete a request, so if we don't even have time left for the idle process, we would overrun the slice in any case. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
1 files changed, 9 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index a592afcf1e6..069a61017c0 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1093,6 +1093,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
if (!cic || !atomic_read(&cic->ioc->nr_tasks))
+ /*
+ * If our average think time is larger than the remaining time
+ * slice, then don't idle. This avoids overrunning the allotted
+ * time slice.
+ */
+ if (sample_valid(cic->ttime_samples) &&
+ (cfqq->slice_end - jiffies < cic->ttime_mean))
+ return;