From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>, Jan Kara <jack@suse.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
linux-kernel@vger.kernel.org, Miao Xie <miaoxie@huawei.com>,
kernel-team@fb.com
Subject: Re: [PATCH block/for-4.7-fixes] writeback: use higher precision calculation in domain_dirty_limits()
Date: Mon, 30 May 2016 08:55:10 -0600 [thread overview]
Message-ID: <574C544E.70905@kernel.dk> (raw)
In-Reply-To: <20160527183446.GS23194@mtj.duckdns.org>
On 05/27/2016 12:34 PM, Tejun Heo wrote:
> 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()")
Queued up for this series, with the minor comment tweak that Jan suggested.
--
Jens Axboe
prev parent reply other threads:[~2016-05-30 14:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <57333E75.3080309@huawei.com>
2016-05-12 1:11 ` [BUG]Writeback Cgroup/Dirty Throttle: very small buffered write thoughput caused by writeback cgroup and dirty thottle Miao Xie
2016-05-12 15:32 ` Tejun Heo
2016-05-13 6:11 ` Miao Xie
2016-05-27 18:24 ` Tejun Heo
2016-05-27 18:34 ` [PATCH block/for-4.7-fixes] writeback: use higher precision calculation in domain_dirty_limits() Tejun Heo
2016-05-30 8:05 ` Jan Kara
2016-05-30 14:55 ` Jens Axboe [this message]
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