AMD EPYC Performance Testing with systemd

Re:AMD EPYC Performance Testing with systemd by imtringued on Thursday July 12, 2018 @06:30PM (#17519157)

There is no such thing as no I/O.

If you're latency bound by the round trip to main memory then SMT will still have a noticeable benefit. The most important thing it can't help with is if you are compute bound.

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Re:AMD EPYC Performance Testing with systemd by BeeOnRope on Thursday July 12, 2018 @09:31PM (#17519916)

Nobody calls "trips to memory" I/O though. Yes SMT can have a benefit but the OP was asking about the case with more threads than logical cores, so SMT is already maxed out (assuming all threads are CPU bound).

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Re:AMD EPYC Performance Testing with systemd by rbanffy on Friday July 13, 2018 @08:36AM (#17522379)

> SMT will still have a noticeable benefit

YMMV. SMT usually halves the cache size usable by each thread. If your memory access is heavily local, enabling SMT can hurt your performance.

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