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authorJosef Bacik <josef@toxicpanda.com>2018-09-28 19:45:43 +0200
committerJens Axboe <axboe@kernel.dk>2018-09-28 19:47:32 +0200
commit451bb7c3319739997d2e5a2527aef62d1f9200ac (patch)
tree93d5da9e9d960a47b57a1fe661c3be6a34aa4be2 /drivers/xen
parentblk-iolatency: use a percentile approache for ssd's (diff)
downloadlinux-451bb7c3319739997d2e5a2527aef62d1f9200ac.tar.xz
linux-451bb7c3319739997d2e5a2527aef62d1f9200ac.zip
blk-iolatency: keep track of previous windows stats
We apply a smoothing to the scale changes in order to keep sawtoothy behavior from occurring. However our window for checking if we've missed our target can sometimes be lower than the smoothing interval (500ms), especially on faster drives like ssd's. In order to deal with this keep track of the running tally of the previous intervals that we threw away because we had already done a scale event recently. This is needed for the ssd case as these low latency drives will have bursts of latency, and if it happens to be ok for the window that directly follows the opening of the scale window we could unthrottle when previous windows we were missing our target. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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