Re: AIM9 slowdowns between 2.6.11 and 2.6.12-rc1 (probably false positive)

[Mel Gorman <mel@csn.ul.ie>]

On Sun, 3 Apr 2005, Dave Hansen wrote:

> On Sun, 2005-04-03 at 15:37 +0100, Mel Gorman wrote:
> > While testing the page placement policy patches on 2.6.12-rc1, I noticed
> > that aim9 is showing significant slowdowns on page allocation-related
> > tests. An excerpt of the results is at the end of this mail but it shows
> > that page_test is allocating 18000 less pages.
> >
> > I did not check who has been recently changing the buddy allocator but
> > they might want to run a benchmark or two to make sure this is not
> > something specific to my setup.
>
> Can you get some kernel profiles to see what, exactly, is causing the
> decreased performance?  Also, what kind of system do you have?  Does
> backing this out help?  If not, can you test some BK snapshots to see
> when this started occurring?
>
> http://linus.bkbits.net:8080/linux-2.5/cset@422de02c1628MP_noKSum9sGlTaC-Q
>

The machine is a quad xeon with P III 733 processors. I don't have profile
information available as I wasn't collecting as I went along. However,
backing out the patch made little difference

However, I reran the test on 2.6.11 and this time the performance
difference was a lot less. Something else must have been happening when I
collected the first set of poor results. I'll revisit this when I'm next
working on kernel stuff and see can I reproduce it again reliably.

-- 
Mel Gorman
Part-time Phd Student                          Java Applications Developer
University of Limerick                         IBM Dublin Software Lab
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