Messages in this thread | | | Date | Mon, 6 Feb 2006 09:51:55 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/5] cpuset memory spread basic implementation |
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* Paul Jackson <pj@sgi.com> wrote:
> Ingo asked: > > so in practice, the memory spreading is in fact a global setting, used > > by all cpusets that matter? > > I don't know if that is true or not. > > I'll have to ask my field engineers, who actually have experience > with a variety of customer workloads. > > ... well, I do have partial knowledge of this. > > When I was coding this, I suggested that instead of picking some of the > slab caches to memory spread, we pick them all, as that would be easier > to code. > > That suggestion was shot down by others more experienced within SGI, > as some slab caches hold what is essentially per-thread data, that is > fairly hot in the thread context that allocated it. Spreading that > data would quite predictably increase cross-node bus traffic, which is > bad.
yes, but still that is a global attribute: we know that those slabs are fundamentally per-thread. They wont ever be non-per-thread. So the decision could be made via a per-slab attribute, that is picked by kernel developers (initially you). The pagecache would be spread-out if this .config option is specified. This makes it a much cleaner static 'kernel fairness policy' thing, instead of a fuzzier userspace thing.
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