Subject: Re: [PATCH]: Free pages from local pcp lists under tight memory
	conditions
From: Rohit Seth <rohit.seth@intel.com>
To: Andrew Morton <akpm@osdl.org>
Cc: clameter@engr.sgi.com, torvalds@osdl.org, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org
In-Reply-To: <20051123132647.257710b9.akpm@osdl.org>
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Organization: Intel 
Date: Wed, 23 Nov 2005 13:40:48 -0800
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On Wed, 2005-11-23 at 13:26 -0800, Andrew Morton wrote:
> Rohit Seth <rohit.seth@intel.com> wrote:
> >
> > > I don't think Martin was able to demonstrate much benefit from the lock
> > > contention reduction on 16-way NUMAQ either.
> > > 
> > > So I dithered for months and it was a marginal merge, so it's appropriate
> > > to justify the continued presence of the code.
> > > 
> > 
> > May be the limits on the number of pages hanging on the per_cpu_pagelist
> > was (or even now is) too small (for them to give any meaningful gain).
> > May be we should have more physical contiguity in each of these pcps to
> > give better cache spread.  
> 
> Could be.  The initial settings were pretty arbitrary - I assumed that
> someone would get in and tune them up, but nothing much happened.  Perhaps
> we should expose the thresholds in /proc/sys/vm so they're easier to play
> with.

Most certainly.  If I had a patch ready...I would have given you one
right away :-)  Though I will work on it...

It surely is unfortunate that we have not digged deeper into this area
(in terms of optimizations)....  

-rohit

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