Re: [PATCH 2/2] mm, memcg: Optionally disable memcg by default using Kconfig

[Mel Gorman <mgorman@suse.de>]

On Wed, May 20, 2015 at 12:24:21PM -0400, Johannes Weiner wrote:
> > 
> > Low thread counts get a small boost but it's within noise as memcg overhead
> > does not dominate. It's not obvious at all at higher thread counts as other
> > factors cause more problems. The overall breakdown of CPU usage looks like
> > 
> >                4.0.0       4.0.0
> >         chargefirst-v2r1disable-v2r1
> > User           41.81       41.45
> > System        407.64      405.50
> > Elapsed       128.17      127.06
> 
> This is a worst case microbenchmark doing nothing but anonymous page
> faults (with THP disabled), and yet the performance difference is in
> the noise.  I don't see why we should burden the user with making a
> decision that doesn't matter in theory, let alone in practice.
> 
> We have CONFIG_MEMCG and cgroup_disable=memory, that should be plenty
> for users that obsess about fluctuation in the noise.  There is no
> reason to complicate the world further for everybody else.

FWIW, I agree and only included this patch because I said I would
yesterday. After patch 1, there is almost no motivation to disable memcg
at all let alone by default.

-- 
Mel Gorman
SUSE Labs

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