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Subject: Re: [hwloc-devel] Memory affinity
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2011-02-28 16:18:11


Le 28/02/2011 21:47, David Singleton a écrit :
> I dont think you can avoid the problem. Unless it has changed very
> recently, Linux swapin_readahead is the main culprit in messing with
> NUMA locality on that platform. Faulting a single page causes 8 or 16
> or whatever contiguous pages to be read from swap. An arbitrary
> contiguous range of pages in swap may not even come from the same
> process far less the same NUMA node. My understanding is that since
> there is no NUMA info with the swap entry, the only policy that can be
> applied to is that of the faulting vma in the faulting process. The
> faulted page will have the desired NUMA placement but possibly not the
> rest. So swapping mixes different process' NUMA policies leading to a
> "NUMA diffusion process".

Ah good point! So Jeff has to hope that pages of different processes
won't be highly mixed in the swap partition, good luck :)

Brice