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SubjectRe: [patch v4 0/18] sched: simplified fork, release load avg and power awareness scheduling
On 01/24/2013 11:07 PM, Alex Shi wrote:
> On 01/24/2013 05:44 PM, Borislav Petkov wrote:
>> On Thu, Jan 24, 2013 at 11:06:42AM +0800, Alex Shi wrote:
>>> Since the runnable info needs 345ms to accumulate, balancing
>>> doesn't do well for many tasks burst waking. After talking with Mike
>>> Galbraith, we are agree to just use runnable avg in power friendly
>>> scheduling and keep current instant load in performance scheduling for
>>> low latency.
>>> So the biggest change in this version is removing runnable load avg in
>>> balance and just using runnable data in power balance.
>>> The patchset bases on Linus' tree, includes 3 parts,
>>> ** 1, bug fix and fork/wake balancing clean up. patch 1~5,
>>> ----------------------
>>> the first patch remove one domain level. patch 2~5 simplified fork/wake
>>> balancing, it can increase 10+% hackbench performance on our 4 sockets
>>> SNB EP machine.
>> Ok, I see some benchmarking results here and there in the commit
>> messages but since this is touching the scheduler, you probably would
>> need to make sure it doesn't introduce performance regressions vs
>> mainline with a comprehensive set of benchmarks.
> Thanks a lot for your comments, Borislav! :)
> For this patchset, the code will just check current policy, if it is
> performance, the code patch will back to original performance code at
> once. So there should no performance change on performance policy.
> I once tested the balance policy performance with benchmark
> kbuild/hackbench/aim9/dbench/tbench on version 2, only hackbench has a
> bit drop ~3%. others have no clear change.
>> And, AFAICR, mainline does by default the 'performance' scheme by
>> spreading out tasks to idle cores, so have you tried comparing vanilla
>> mainline to your patchset in the 'performance' setting so that you can
>> make sure there are no problems there? And not only hackbench or a
>> microbenchmark but aim9 (I saw that in a commit message somewhere) and
>> whatever else multithreaded benchmark you can get your hands on.
>> Also, you might want to run it on other machines too, not only SNB :-)
> Anyway I will redo the performance testing on this version again on all
> machine. but doesn't expect something change. :)

Just rerun some benchmarks: kbuild, specjbb2005, oltp, tbench, aim9,
hackbench, fileio-cfq of sysbench, dbench, aiostress, multhreads
loopback netperf. on my core2, nhm, wsm, snb, platforms. no clear
performance change found.

I also tested balance policy/powersaving policy with above benchmark,
found, the specjbb2005 drop much 30~50% on both of policy whenever with
openjdk or jrockit. and hackbench drops a lots with powersaving policy
on snb 4 sockets platforms. others has no clear change.

>> And what about ARM, maybe someone there can run your patchset too?
>> So, it would be cool to see comprehensive results from all those runs
>> and see what the numbers say.
>> Thanks.


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