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>
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@ -366,7 +366,7 @@ static void check_scale_change(struct iolatency_grp *iolat)
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* scale down event.
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*/
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samples_thresh = lat_info->nr_samples * 5;
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samples_thresh = div64_u64(samples_thresh, 100);
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samples_thresh = max(1ULL, div64_u64(samples_thresh, 100));
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if (iolat->nr_samples <= samples_thresh)
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return;
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}
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