linux-kernel - Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough

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Date:	Fri, 14 Oct 2011 09:19:21 -0500
From:	Dimitri Sivanich <sivanich@....com>
To:	Christoph Lameter <cl@...two.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH] Reduce vm_stat cacheline contention in
 __vm_enough_memory

On Fri, Oct 14, 2011 at 08:57:16AM -0500, Christoph Lameter wrote:
> On Fri, 14 Oct 2011, Dimitri Sivanich wrote:
> 
> > Testing on a smaller machine with 46 writer threads in parallel (my original
> > test used 120).
> >
> > Looks as though cache-aligning and padding the end of the vm_stat array
> > results in a ~150 MB/sec speedup.  This is a nice improvement for only 46
> > writer threads, though it's not the full ~250 MB/sec speedup I get from
> > setting OVERCOMMIT_NEVER.
> 
> Add to this the increase in the deltas for the ZVCs and change the stat
> interval to 10 sec?

Increasing the ZVC deltas (threshold value in calculate*threshold == 125)
does -seem- to give a small speedup in this case (maybe as much as 50 MB/sec?).

Changing the stat interval to 10 seconds still has no effect, with or without
the ZVC delta change.

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