Messages in this thread | | | Date | Tue, 7 Feb 2006 14:15:25 -0800 | From | Andrew Morton <> | Subject | Re: [rfc][patch] sched: remove smpnice |
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Con Kolivas <kernel@kolivas.org> wrote: > > On Wednesday 08 February 2006 01:28, Nick Piggin wrote: > > I'd like to get some comments on removing smpnice for 2.6.16. I don't > > think the code is quite ready, which is why I asked for Peter's additions > > to also be merged before I acked it (although it turned out that it still > > isn't quite ready with his additions either). > > > > Basically I have had similar observations to Suresh in that it does not > > play nicely with the rest of the balancing infrastructure (and raised > > similar concerns in my review). > > > > The samples (group of 4) I got for "maximum recorded imbalance" on a 2x2 > > > > SMP+HT Xeon are as follows: > > | Following boot | hackbench 20 | hackbench 40 > > > > -----------+----------------+---------------------+--------------------- > > 2.6.16-rc2 | 30,37,100,112 | 5600,5530,6020,6090 | 6390,7090,8760,8470 > > +nosmpnice | 3, 2, 4, 2 | 28, 150, 294, 132 | 348, 348, 294, 347 > > > > Hackbench raw performance is down around 15% with smpnice (but that in > > itself isn't a huge deal because it is just a benchmark). However, the > > samples show that the imbalance passed into move_tasks is increased by > > about a factor of 10-30. I think this would also go some way to > > explaining latency blips turning up in the balancing code (though I > > haven't actually measured that). > > > > We'll probably have to revert this in the SUSE kernel. > > > > The other option for 2.6.16 would be to fast track Peter's stuff, which > > I could put some time into... but that seems a bit risky at this stage > > of the game. > > > > I'd like to hear any other suggestions though. Patch included to aid > > discussion at this stage, rather than to encourage any rash decisions. > > I see the demonstrable imbalance but I was wondering if there is there a real > world benchmark that is currently affected? >
Well was any real-world workload (or benchmark) improved by the smpnice change?
Because if we have one workload which slowed and and none which sped up, it's a pretty easy decision.. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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