Messages in this thread | | | From | Nick Piggin <> | Subject | Re: [PATCH 00/10] x86: Reduce memory and intra-node effects with large count NR_CPUs | Date | Wed, 16 Jan 2008 18:34:39 +1100 |
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On Monday 14 January 2008 22:30, Andi Kleen wrote:
> In general there are more scaling problems like this (e.g. it also doesn't > make sense to scale kernel threads for each CPU thread for example).
I think in a lot of ways, per-CPU kernel threads scale OK. At least they should mostly be dynamic, so they don't require overhead on smaller systems. On larger systems, I don't know if there are too many kernel problems with all those threads (except for userspace tools sometimes don't report well).
And I think making them per-CPU can be much easier than tuning some arbitrary algorithm to get a mix between parallelism and footprint.
For example, I'm finding that it might actually be worthwhile to move some per-node and dynamically-controlled thread creation over to the basic per-CPU scheme because of differences in topologies...
Anyway, that's just an aside.
Oh, just while I remember it also, something funny is that MAX_NUMNODES can be bigger than NR_CPUS on x86. I guess one can have CPUless nodes, but wouldn't it make sense to have an upper bound of NR_CPUS by default?
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