Re: [PATCH]: Free pages from local pcp lists under tight memoryconditions

From: Rohit Seth
Date: Wed Nov 23 2005 - 16:33:41 EST

On Wed, 2005-11-23 at 13:26 -0800, Andrew Morton wrote:
> Rohit Seth <rohit.seth@xxxxxxxxx> 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)....


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