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SubjectRe: [patch] SLQB slab allocator (try 2)
On Mon, Feb 16, 2009 at 09:17:58PM +0200, Pekka Enberg wrote:
> Hi Mel,
>
> Mel Gorman wrote:
>> I haven't done much digging in here yet. Between the large page bug and
>> other patches in my inbox, I haven't had the chance yet but that doesn't
>> stop anyone else taking a look.
>
> So how big does an improvement/regression have to be not to be
> considered within noise? I mean, I randomly picked one of the results
> ("x86-64 speccpu integer tests") and ran it through my "summarize"
> script and got the following results:
>
> min max mean std_dev
> slub 0.96 1.09 1.01 0.04
> slub-min 0.95 1.10 1.00 0.04
> slub-rvrt 0.90 1.08 0.99 0.05
> slqb 0.96 1.07 1.00 0.04
>

Well, it doesn't make a whole pile of sense to get the average of these ratios
or the deviation between them. Each of the tests behave very differently. I'd
consider anything over 0.5% significant but I also have to admit I wasn't
doing multiple runs this time due to the length of time it takes. In a
previous test, I ran them 3 times each and didn't spot large deviations.

> Apart from slub-rvrt (which seems to be regressing, interesting) all the
> allocators seem to perform equally well. Hmm?
>

For this stuff, they are reasonably close but I don't believe thye are
allocator intensive either. SPEC CPU was brought up as a workload HPC people
would care about. Bear in mind it's also not testing NUMA or CPU scalability
really well. It's one data-point. netperf is a much more allocator intensive
workload.

> Btw, Yanmin, do you have access to the tests Mel is running (especially
> the ones where slub-rvrt seems to do worse)? Can you see this kind of
> regression? The results make we wonder whether we should avoid reverting
> all of the page allocator pass-through and just add a kmalloc cache for
> 8K allocations. Or not address the netperf regression at all. Double-hmm.
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


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