[Beowulf] Again about NUMA (numactl and taskset)
kus at free.net
Wed Jun 25 09:34:53 PDT 2008
Let me assume now the following situation. I have OpenMP-parallelized
application which have the number of processes equal to number of CPU
cores per server. And let me assume that this application uses not too
more virtual memory, so all the real memory used may be placed in RAM
of *one* node.
It's not the abstract question - a lot of Gaussian-03 jobs we have fit
to this situation, and all the 8 cores for dual socket quad core
Opteron server will be "well loaded".
Is it right that all the application memory (w/o using of numactl)
will be allocated (by Linux kernel) in *one* node ? Then only one
memory controller will be used.
OK, then if I have the same server but w/2 times more small memory
size (it's enough for run of this Gaussian-03 job !) and DIMMs are
populating both nodes, then the performance of this server will be
higher ! - because both memory controllers (and therefore more memory
channels) will work simultaneously.
Is it right - that more cheap server will have higher performance for
like cases ??
Computer Assistance to Chemical Research Center
Zelinsky Institute of Organic Chemistry
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