Messages in this thread | | | Date | Tue, 7 Apr 2009 09:56:21 +0200 | From | Andi Kleen <> | Subject | Re: Off topic: Numactl "distance" wrong |
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On Tue, Apr 07, 2009 at 09:40:56AM +0200, Brice Goglin wrote: > Andi Kleen wrote: > >> Well, some user-space application may use these distances > >> to improve their binding. > >> > > > > I'm not aware of any that does. > > We have some people here that would like to use it ideally. But they > know numa distances is almost never available, so they don't really look > at using them...
From my experience and from talking at people they tend to have enough trouble getting the basic NUMA tunings done, without caring about such (arcane) details.
> > > If it's true then the correct place would be to fix the BIOS. > > > > Come on, you know it's not going to happen for 99.9% on the existing > opteron boxes. We have many hardware quirks in the kernel, I don't see > why this numa distance problem would not deserve its own work around.
The systems where it makes a large difference typically have them anyways.
Anyways if you really want you can ask Len for a way to override SLIT tables at boot time (similar to the mechanism for MADTs), but I suspect he wouldn't be particularly enthuiastic. Also it's a little more tricky than for normal MADTs because SLIT parsing happens very early.
> By the way, anybody looked at this on Nehalem boxes ?
Current Nehalem boxes are all fully connected, so 10/20 (or sometimes scaled to trigger the zone fallback workaround) is the correct answer and you don't get any benefits from magic in this area.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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