linux-kernel - Re: [patch 0/7] cpuset writeback throttling

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Message-Id: <20081106103455.f3277a72.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 6 Nov 2008 10:34:55 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, npiggin@...e.de,
	Christoph Lameter <cl@...ux-foundation.org>, dfults@....com,
	linux-kernel@...r.kernel.org, containers@...ts.osdl.org,
	Paul Menage <menage@...gle.com>,
	Andrea Righi <righi.andrea@...il.com>
Subject: Re: [patch 0/7] cpuset writeback throttling

On Wed, 5 Nov 2008 14:04:42 -0800 (PST)
David Rientjes <rientjes@...gle.com> wrote:

> > So the world wouldn't end if we just didn't merge it.  Those users
> > stick with their workarounds and the kernel remains simpler and
> > smaller.
> > 
> 
> Agreed.  This patchset is admittedly from a different time when cpusets 
> was the only relevant extension that needed to be done.
> 
BTW, what is the problem this patch wants to fix ?
  1. avoid slow-down of memory allocation by triggering write-out earlier.
  2. avoid OOM by throttoling dirty pages.

About 1, memcg's diry_ratio can help if mounted as
   mount -t cgroup none /somewhere/  -o cpuset,memory
(If the user can accept overheads of memcg.)
If implemented.

About 2, A Google guy posted OOM handler cgroup to linux-mm.

> > How do we work out which is the best choice here?  I don't have enough
> > information to do this.
> > 
> 
> If we are to support memcg-specific dirty ratios, that requires the 
> aforementioned statistics to be collected so that the calculation is even 
> possible.  The series at 
> 
> 	http://marc.info/?l=linux-kernel&m=122123225006571
> 	http://marc.info/?l=linux-kernel&m=122123241106902
> 
yes. we(memcg) need this kind of.

> is a step in that direction, although I'd prefer to see NR_UNSTABLE_NFS to 
> be extracted separately from MEM_CGROUP_STAT_FILE_DIRTY so 
> throttle_vm_writeout() can also use the new statistics.
> 
Thank you for input.

Thanks,
-Kame


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