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Joe Thornber authored
IO tracking used to throttle writebacks when the origin device is busy. Even if all the IO is going to the fast device, writebacks can significantly degrade performance. So track all IO to gauge whether the cache is busy or not. Otherwise, synthetic IO tests (e.g. fio) that might send all IO to the fast device wouldn't cause writebacks to get throttled. Signed-off-by:
Joe Thornber <ejt@redhat.com> Signed-off-by:
Mike Snitzer <snitzer@redhat.com>
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