On Wed, 30 Jul 2008 18:23:18 +0100 Mel Gorman [off-list ref] wrote:

On (30/07/08 01:43), Andrew Morton didst pronounce:

quoted

On Mon, 28 Jul 2008 12:17:10 -0700 Eric Munson [off-list ref] wrote:

quoted

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).