writeback, cgroup: Adjust WB_FRN_TIME_CUT_DIV to accelerate foreign inode switching
WB_FRN_TIME_CUT_DIV is used to tell the foreign inode detection logic to ignore short writeback rounds to prevent getting confused by a burst of short writebacks. The parameter is currently 2 meaning that anything smaller than half of the running average writback duration will be ignored. This is unnecessarily aggressive. The detection logic uses 16 history slots and is already reasonably protected against some short bursts confusing it and the current parameter can lead to tens of seconds of missed detection depending on the writeback pattern. Let's change the parameter to 8, so that it only ignores writeback with are smaller than 12.5% of the current running average. v2: Add comment explaining what's going on with the foreign detection parameters. Reviewed-by:Jan Kara <jack@suse.cz> Signed-off-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
Jens Axboe <axboe@kernel.dk>
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b8e24a93
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