On Fri, 2013-07-05 at 12:33 +0800, Michael Wang wrote:
> On 07/05/2013 12:08 PM, Mike Galbraith wrote:
> [snip]
> >>
> >> Wow, I used to think such issue is very hard to be tracked by
> >> benchmarks, is this regression stable?
> >
> > Yeah, seems to be. I was curious as to why you saw an improvement to
> > hackbench, didn't seem there should be any, so though I'd try it on my
> > little box on the way to a long weekend. The unexpected happened.
>
> Oh, I think I failed to explain things clearly in comments...
>
> It's not the patch who bring 15% benefit to hackbench, but the
> wake-affine stuff itself.
>
> In the prev-test, I removed the whole stuff and find that hackbench
> dropped 15%, which means with wake-affine enabled, we will gain 15%
> benefit (and that's actually the reason why we don't kill the stuff).
Ah.
> And this idea is try to not harm that 15% benefit, and meanwhile regain
> the pgbench lost performance, thus, apply this patch to mainline won't
> improve hackbench performance, but improve pgbench performance.
>
> But this regression is really unexpected... I could hardly believe it's
> just caused by cache issue now, since the number is not small (10% at
> most?).
>
> Have you tried to use more loops and groups? will that show even bigger
> regressions?
Nope, less on either side.
hackbench -g 100 -l 1000
avg
3.10.0-regress 21.895 21.564 21.777 21.958 22.093 21.857
1.000
3.10.0-regressx 22.844 23.268 23.056 23.231 22.375 22.954
1.050
hackbench -g 1 -l 100000
avg
3.10.0-regress 29.913 29.711 30.395 30.213 30.236 30.093
1.000
3.10.0-regressx 30.392 31.003 30.728 31.008 30.389 30.704
1.020
> BTW, is this the results of 10 group and 40 sockets == 400 tasks?
Yeah, stock.
Off to do some body/mind tuning. Bavarian mushrooms don't hide as well
as memory access thingies.. and I can still out run 'em.
-Mike
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