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SubjectRe: Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue()
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On Tue, 2012-10-02 at 07:51 +0100, Mel Gorman wrote: 
> I'm going through old test results to see could I find any leftover
> performance regressions that have not yet been fixed (most have at this point
> or at least changed in such a way to make a plain revert impossible). One
> major regression still left is with netperf UDP_STREAM regression. Bisection
> points the finger straight at 518cd623 (sched: Only queue remote wakeups
> when crossing cache boundaries). Problem was introduced between 3.2 and
> 3.3, current kernel still sucks as the following results show.
>
> NETPERF UDP
> 3.3.0 3.3.0 3.6.0
> vanilla revert-518cd623 vanilla
> Tput 64 328.38 ( 0.00%) 436.58 ( 32.95%) 312.51 ( -4.83%)
> Tput 128 661.43 ( 0.00%) 869.88 ( 31.52%) 625.70 ( -5.40%)
> Tput 256 1310.27 ( 0.00%) 1724.45 ( 31.61%) 1243.65 ( -5.08%)
> Tput 1024 5466.85 ( 0.00%) 6601.43 ( 20.75%) 4838.86 (-11.49%)
> Tput 2048 10885.95 ( 0.00%) 12694.06 ( 16.61%) 9161.75 (-15.84%)
> Tput 3312 15930.33 ( 0.00%) 19327.67 ( 21.33%) 14106.26 (-11.45%)
> Tput 4096 18025.47 ( 0.00%) 22183.12 ( 23.07%) 16636.01 ( -7.71%)
> Tput 8192 30076.42 ( 0.00%) 37280.86 ( 23.95%) 28575.84 ( -4.99%)
> Tput 16384 47742.12 ( 0.00%) 56123.21 ( 17.55%) 46060.57 ( -3.52%)

Hm, 518cd623 fixed up the troubles I saw. How exactly are you running
this?

-Mike



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