Messages in this thread | | | Date | Mon, 6 Feb 2006 19:43:30 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/5] cpuset memory spread basic implementation |
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* Andi Kleen <ak@suse.de> wrote:
> > > If you have a much worse worst case NUMA factor it might be different, > > > but even there it would be a good idea to at least spread it out > > > to nearby nodes. > > > > I dont understand you here. What would be the benefit of selecting more > > distant memory over local? I can only imagine that this would be > > beneficial if we know that the data would be used later by other > > processes. > > The benefit would be to not fill up the local node as quickly when you > do something IO (or dcache intensive). And on contrary when you do > something local memory intensive on that node then you won't need to > throw away all the IO caches if they are already spread out. > > The kernel uses of these cached objects are not really _that_ latency > sensitive and not that frequent so it makes sense to spread it out a > bit to nearby nodes.
I'm not sure i agree. If a cache isnt that important, then there wont be that much of them (hence they cannot interact with user pages that much), and it wont be used that frequently -> the VM will discard it faster. If there's tons of dentries and inodes and pagecache around, then there must be a reason it's around: it was actively used. In that case we should spread them out only if we know in advance that their use is global, not local - and we should default to local.
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