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Date: Mon, 27 Nov 2017 09:52:20 +0100
From: Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH] mm: print a warning once the vm dirtiness settings is
 illogical
Message-ID: <20171127085220.kf6gyksfy276mkk6@dhcp22.suse.cz>
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To: Yafang Shao <laoar.shao@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>, Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>, Linux MM <linux-mm@kvack.org>, fcicq@fcicq.net

On Mon 27-11-17 16:49:34, Yafang Shao wrote:
> 2017-11-27 16:37 GMT+08:00 Michal Hocko <mhocko@suse.com>:
> > On Mon 27-11-17 16:32:42, Yafang Shao wrote:
> >> 2017-11-27 16:29 GMT+08:00 Yafang Shao <laoar.shao@gmail.com>:
[...]
> >> > It will help us to find the error if we don't change these values like this.
> >> >
> >>
> >> And actually it help us find another issue that when availble_memroy
> >> is too small, the thresh and bg_thresh will be 0, that's absolutely
> >> wrong.
> >
> > Why is it wrong?
> > --
> 
> For example, the writeback threads will be wakeup on every write.
> I don't think it is meaningful to wakeup the writeback thread when the
> dirty pages is very low.

Well, this is a corner situation when we are out of memory basically.
Doing a wake up on the flusher is the least of your problem. So _why_
exactly is this is problem?
-- 
Michal Hocko
SUSE Labs

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