Messages in this thread | | | Date | Wed, 28 Oct 2009 19:00:10 -0500 | Subject | Re: Hyperthreading on 4 core CPU DECREASES performance??? | From | Igor Chudov <> |
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On Wed, Oct 28, 2009 at 5:24 PM, Alan Cox <alan@lxorguk.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.
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