[Beowulf] Again about NUMA (numactl and taskset)

[Håkon Bugge]

Hi Mark,

At 17:25 23.06.2008, Mark Hahn wrote:

>>5) In which cases is it reasonable to switch on 
>>"Node memory interleaving" (in BIOS) for the 
>>application which uses more memory than is presented on the node ?
>
>I leave it off, since numactl --interleave lets 
>you get the same effect from user-space.  I'm 
>not sure I've ever seen it be a win.

numactl --interleave will for sure use (at least) 
page resolution performing the interleave. In my 
fantasy, I imagine the hardware interleave to be 
on a cache-line boundary. If that is the case, 
you might see differences though, for example if 
the threads/processes tend to generate cache 
misses to a single page, but different lines 
within that page. Probably an unlikely scenario for real applications...



Håkon




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