linux-kernel - Re: kswapd hogging in lowmem

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Message-ID: <5502F9BC.2020001@redhat.com>
Date:	Fri, 13 Mar 2015 10:52:44 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Vaibhav Shinde <v.bhav.shinde@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: kswapd hogging in lowmem_shrink

On 03/13/2015 10:25 AM, Vaibhav Shinde wrote:
> 
> On low memory situation, I see various shrinkers being invoked, but in
> lowmem_shrink() case, kswapd is found to be hogging for around 150msecs.
> 
> Due to this my application suffer latency issue, as the cpu was not
> released by kswapd0.
> 
> I took below traces with vmscan events, that show lowmem_shrink taking
> such long time for execution.

This is the Android low memory killer, which kills the
task with the lowest priority in the system.

The low memory killer will iterate over all the tasks
in the system to identify the task to kill.

This is not a problem in Android systems, and other
small systems where this piece of code is used.

What kind of system are you trying to use the low
memory killer on?

How many tasks are you running?

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