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authorTejun Heo <tj@kernel.org>2016-05-27 14:34:46 -0400
committerJens Axboe <axboe@fb.com>2016-05-30 08:54:40 -0600
commit62a584fe05eef1f80ed49a286a29328f1a224fb9 (patch)
treecf34bae00e267a9e5fb94a70d7f24f893d325e6b /block/blk-mq.c
parentb02b1fbdd338f70e49efa9ca9899214134526701 (diff)
writeback: use higher precision calculation in domain_dirty_limits()
As vm.dirty_[background_]bytes can't be applied verbatim to multiple cgroup writeback domains, they get converted to percentages in domain_dirty_limits() and applied the same way as vm.dirty_[background]ratio. However, if the specified bytes is lower than 1% of available memory, the calculated ratios become zero and the writeback domain gets throttled constantly. Fix it by using per-PAGE_SIZE instead of percentage for ratio calculations. Also, the updated DIV_ROUND_UP() usages now should yield 1/4096 (0.0244%) as the minimum ratio as long as the specified bytes are above zero. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Miao Xie <miaoxie@huawei.com> Link: http://lkml.kernel.org/g/57333E75.3080309@huawei.com Cc: stable@vger.kernel.org # v4.2+ Fixes: 9fc3a43e1757 ("writeback: separate out domain_dirty_limits()") Reviewed-by: Jan Kara <jack@suse.cz> Adjusted comment based on Jan's suggestion. Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq.c')
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