SMT enabled on ACAN001 but not on ACAN003?

SMT enabled on ACAN001 but not on ACAN003?

Bild des Benutzers Lars Bergstrom

Just curious -- is there a reason that SMT is enabled (so we get 64 processors from /proc/cpuinfo) on the login server, ACAN001, but it's disabled and we get 32 on ACAN003?

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Bild des Benutzers Mike Pearce (Intel)
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Yes that's accurate -using 64-threads on the batch nodes (acano02 & acano03), we have seen does not really by you much more performance, particularly when running jobs that utilize the same functional units in the core. You mayeven see a degredation in performance.

So we have enabledonly the physicalcores on the batch nodes. This may simplify the scheduling of threads on the batch nodes, as only physical cores are available.

Ifyou would like to get SMT results or see if you workloadimproves using hyperthreading, then please use the login node (acano01)

Bild des Benutzers Lars Bergstrom

Thanks -- that makes sense! And it's also my memory that there was often a performance drop with SMT enabled for processes that run at 100% utilization, though the only evaluation I've done is back six or seven years ago, when it was HyperThreading. I'll try not to abuse the login node when others are on it. I will run some tests, though, to see how loading up the cores with additional VM threads affects our performance.

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