linux-kernel - Re: [PATCH V2] nommu: add anonymous page memcg accounting

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Date:	Wed, 20 Oct 2010 09:17:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	steve@...idescorp.com
Cc:	balbir@...ux.vnet.ibm.com, linux-mm@...ck.org, dhowells@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] nommu: add anonymous page memcg accounting

On Tue, 19 Oct 2010 13:24:17 -0500
"Steven J. Magnani" <steve@...idescorp.com> wrote:

> On Tue, 2010-10-19 at 21:18 +0530, Balbir Singh wrote:
> > * Steven J. Magnani <steve@...idescorp.com> [2010-10-19 07:34:14]:
> > 
> > > Add the necessary calls to track VM anonymous page usage (only).
> > > 
> > > V2 changes:
> > > * Added update of memory cgroup documentation
> > > * Clarify use of 'file' to distinguish anonymous mappings
> > > 
> > > Signed-off-by: Steven J. Magnani <steve@...idescorp.com>
> > > ---
> > > diff -uprN a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> > > --- a/Documentation/cgroups/memory.txt	2010-10-05 09:14:36.000000000 -0500
> > > +++ b/Documentation/cgroups/memory.txt	2010-10-19 07:28:04.000000000 -0500
> > > @@ -34,6 +34,7 @@ Current Status: linux-2.6.34-mmotm(devel
> > > 
> > >  Features:
> > >   - accounting anonymous pages, file caches, swap caches usage and limiting them.
> > > +   NOTE: On NOMMU systems, only anonymous pages are accounted.
> > >   - private LRU and reclaim routine. (system's global LRU and private LRU
> > >     work independently from each other)
> > >   - optionally, memory+swap usage can be accounted and limited.
> > > @@ -640,7 +641,30 @@ At reading, current status of OOM is sho
> > >  	under_oom	 0 or 1 (if 1, the memory cgroup is under OOM, tasks may
> > >  				 be stopped.)
> > > 
> > > -11. TODO
> > > +11. NOMMU Support
> <snip>
> > > +
> > > +At the present time, only anonymous pages are included in NOMMU memory cgroup
> > > +accounting.
> > 
> > What is the reason for tracking just anonymous memory?
> 
> Tracking more than that is beyond my current scope, and perhaps of
> limited benefit under an assumption that NOMMU systems don't usually
> work with large files. The limitations of the implementation are
> documented, so hopefully anyone who needs more functionality will know
> that they need to implement it.
> 

What happens at reaching limit ? memory can be reclaimed ?

Thanks,
-Kame


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