[Beowulf] Again about NUMA (numactl and taskset)
kus at free.net
Thu Jun 26 12:10:43 EDT 2008
In message from Håkon Bugge <Hakon.Bugge at scali.com> (Thu, 26 Jun 2008
Numastat statistics before Gaussian-03 run (OpenMP, 8 threads, 8
requires 512 Mbytes shared memory plus something more, may be fitted
in memory of any node - I have 8 GB per node, 6- GB free in node0 and
7+ GB free in node1)
Statistics after run:
Unfortunately I don't know, what exactly means this lines !! :-(
(BTW, do somebody know ?!)
But intuitive it looks (taking into account the increase of
numa_hit and local_node values), that the allocation of RAM was
performed from BOTH nodes (and more RAM was allocated from node1
memory - node1 had initially more free RAM).
It is in opposition w/my expectations of "continuous" RAM allocation
from the RAM of one node !
Computer Assistance to Chemical Research
Zelinsky Institute of Organic Chemistry
>At 18:34 25.06.2008, Mikhail Kuzminsky wrote:
>>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 ?
>Guess the answer is, it depends. The memory will be allocated on the
>node where the thread first touching it is running. But you could use
>numastat to investigate the issue.
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