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blk-iolatency: deal with small samples 

There is logic to keep cgroups that haven't done a lot of IO in the most
recent scale window from being punished for over-active higher priority
groups.  However for things like ssd's where the windows are pretty
short we'll end up with small numbers of samples, so 5% of samples will
come out to 0 if there aren't enough.  Make the floor 1 sample to keep
us from improperly bailing out of scaling down.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Josef Bacik 2018-09-28 13:45:41 -04:00 committed by Jens Axboe
parent 9f60511a02
commit 22ed8a93ad
1 changed files with 1 additions and 1 deletions
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block/blk-iolatency.c
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@ -366,7 +366,7 @@ static void check_scale_change(struct iolatency_grp *iolat)
* scale down event.
*/
samples_thresh = lat_info->nr_samples * 5;
samples_thresh = div64_u64(samples_thresh, 100);
samples_thresh = max(1ULL, div64_u64(samples_thresh, 100));
if (iolat->nr_samples <= samples_thresh)
return;
}