Messages in this thread | | | From | Andrew Theurer <> | Subject | Re: How can I optimize a process on a NUMA architecture(x86-64 specifically)? | Date | Mon, 24 May 2004 17:00:57 -0500 |
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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.
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.
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