Re: kswapd hogging in lowmem_shrink

[Vaibhav Shinde <v.bhav.shinde@gmail.com>]

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On Fri, Mar 13, 2015 at 8:22 PM, Rik van Riel <riel@redhat.com> wrote:

> 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?
>
> yes, lowmemorykiller kills the task depending on its oom_score, I am using
a embedded device with 2GB memory, there are task running that cause
lowmemory situation - no issue about it.

But my concern is kswapd takes too long to iterate through all the
processes(lowmem_shrink() => for_each_process()), the time taken is around
150msec, due to which my high priority application suffer system latency
that cause malfunctioning.

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