Messages in this thread | | | Date | Mon, 24 May 2004 18:09:12 -0700 | From | "Brett E." <> | Subject | Re: How can I optimize a process on a NUMA architecture(x86-64 specifically)? |
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Andrew Theurer wrote:
> On Sunday 23 May 2004 09:28, Andi Kleen wrote: > >>On Sat, May 22, 2004 at 05:28:09PM -0700, Bryan O'Sullivan wrote: >> >>>On Fri, 2004-05-21 at 16:42, Brett E. wrote: >>> >>>>Right now, 5 processes are running taking up a good deal of the CPU >>>>doing memory-intensive work(cacheing) and I notice that none of the >>>>processes seem to have CPU affinity. >>> >>>I don't know what kind of system you're running on, but if it's a >>>multi-CPU Opteron, it is normally a sufficient fudge to just use >>>sched_setaffinity to bind individual processes to specific CPUs. The >>>mainline kernel memory allocator does the right thing in that case, and >>>allocates memory locally when it can. >>> >>>You can use the taskset command to get at this from the command line, so >>>you may not even need to modify your code. >> >>Linus also merged the NUMA API support into mainline now with 2.6.7rc1, so >>you can use numactl for more finegrained tuning. > > > FYI Brett, some Opteron systems have a BIOS option to interleave memory. If > you are going to make use of NUMA, I think you want to not interleave. Thanks for the heads up, I just disabled interleaving in the BIOS.
> > Also, if you have a 25% imbalance within a domain/node, the scheduler can have > a tendency to bounce around a task for fairness. That might be why you are > seeing little/no affinity to a cpu (even top might be causing some of this). > Not sure what the threshold is between domains/nodes, but I am curious if it > still happens with CONFIG_NUMA on. If these are long lived cpu bound > processes, I would try to have the number of processes be a multiple of the > number of cpus. I have CONFIG_NUMA on and yes these are long-lived processes(duration is 1 hour). And you and I are on the same wavelength, I'm imagining 3 processes per CPU with apache handing off work to the processes in question. This is on a 1.6ghz 2-way opteron if that matters at all. Hopefully I can make the modifications and test this tomorrow.
Thanks,
Brett
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