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Date: Wed, 30 Jul 2008 10:34:07 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [RFC] [PATCH 0/5 V2] Huge page backed user-space stacks
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Cc: linuxppc-dev@ozlabs.org, Eric Munson <ebmunson@us.ibm.com>,
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On Wed, 30 Jul 2008 18:23:18 +0100 Mel Gorman <mel@csn.ul.ie> wrote:

> On (30/07/08 01:43), Andrew Morton didst pronounce:
> > On Mon, 28 Jul 2008 12:17:10 -0700 Eric Munson <ebmunson@us.ibm.com> wrote:
> > 
> > > Certain workloads benefit if their data or text segments are backed by
> > > huge pages.
> > 
> > oh.  As this is a performance patch, it would be much better if its
> > description contained some performance measurement results!  Please.
> > 
> 
> I ran these patches through STREAM (http://www.cs.virginia.edu/stream/).
> STREAM itself was patched to allocate data from the stack instead of statically
> for the test. They completed without any problem on x86, x86_64 and PPC64
> and each test showed a performance gain from using hugepages.  I can post
> the raw figures but they are not currently in an eye-friendly format. Here
> are some plots of the data though;
> 
> x86: http://www.csn.ul.ie/~mel/postings/stack-backing-20080730/x86-stream-stack.ps
> x86_64: http://www.csn.ul.ie/~mel/postings/stack-backing-20080730/x86_64-stream-stack.ps
> ppc64-small: http://www.csn.ul.ie/~mel/postings/stack-backing-20080730/ppc64-small-stream-stack.ps
> ppc64-large: http://www.csn.ul.ie/~mel/postings/stack-backing-20080730/ppc64-large-stream-stack.ps
> 
> The test was to run STREAM with different array sizes (plotted on X-axis)
> and measure the average throughput (y-axis). In each case, backing the stack
> with large pages with a performance gain.

So about a 10% speedup on x86 for most STREAM configurations.  Handy -
that's somewhat larger than most hugepage-conversions, iirc.

Do we expect that this change will be replicated in other
memory-intensive apps?  (I do).