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Date: Wed, 28 Oct 2009 19:00:10 -0500 From: Igor Chudov <ichudov@...il.com> To: Alan Cox <alan@...rguk.ukuu.org.uk> Cc: linux-kernel@...r.kernel.org Subject: Re: Hyperthreading on 4 core CPU DECREASES performance??? On Wed, Oct 28, 2009 at 5:24 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote: >> This is Ubuntu Hardy, 2.6.24 kernel. I tried the same with 2.6.31, >> with the same effect. >> I would like to know how can I make the scheduler to prefer to spread >> the tasks across physical cores as opposed to bundling two on one core >> and leaving some cores idle. > > The scheduler will try and do balancing for packages and for HT. Make > sure your distribution is built with the SCHED_SMT and SCHED_MC options > enabled. Some of the non-enterprise distirbutions may well not have these > enabled. Yes, for the stock hardy -server and -generic kernel: CONFIG_SCHED_MC=y CONFIG_SCHED_SMT=y > > For hand laying out threads see: man pthread_setaffinity_np > > The win from HT depends a lot on the CPU and also the workload mix. In > some workloads it will decrease performance. OK, I think that I understand. Thanks. So, what you are basically saying is that there is no option to improve this behavior, right? Thanks Alan. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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