linux-kernel - Re: [BUG]Writeback Cgroup/Dirty Throttle: very small buffered write thoughput caused by writeback cgroup and dirty thottle

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Message-ID: <20160527182409.GR23194@mtj.duckdns.org>
Date:	Fri, 27 May 2016 14:24:09 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Miao Xie <miaoxie@...wei.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [BUG]Writeback Cgroup/Dirty Throttle: very small buffered write
 thoughput caused by writeback cgroup and dirty thottle

Hello,

Sorry about the delay.  I forgot about this thread.

On Fri, May 13, 2016 at 02:11:53PM +0800, Miao Xie wrote:
> Better than the kernel without patch. Now the benchmark could reach
> the device bandwidth after 5-8 seconds.  But at the beginning, it
> was still very slow, and its thoughput was only 4MB/s for ~4
> seconds, then it could go up in 1~3 seconds.

I see.  As this fix is needed anyways, I'll send it up.  As for the
ramp-up, it could be normal.  There are estimators which take running
avg and modulate the threshold accordingly and the starting values are
conservative, so a short ramp-up time can be coming from that.

Thanks.

-- 
tejun