How to set $NUM_CPU_CORES

[JohnNeil]

How to I set $NUM_CPU_CORES to control the number of threads started for a multi-threaded benchmark? I thought the following would work but it doesn't:

$ env NUM_CPU_CORES=2 phoronix-test-suite diagnostics | grep NUM_CPU_CORES
NUM_CPU_CORES = 4

[Michael]

How to I set $NUM_CPU_CORES to control the number of threads started for a multi-threaded benchmark? I thought the following would work but it doesn't:

$ env NUM_CPU_CORES=2 phoronix-test-suite diagnostics | grep NUM_CPU_CORES
NUM_CPU_CORES = 4

Hi JohnNeil and welcome. At the moment, NUM_CPU_CORES isn't checked by the environment outside of PTS, but I may end up offering it seeing as a few others have expected similar behavior when wanting to toggle the number of CPU cores/threads exposed for testing. But anyhow, with all current versions of PTS you can use either the PTS_NPROC environment variable or NUMBER_OF_PROCESSORS environment variable to influence the value of NUM_CPU_CORES set by PTS for test scripts. Either of those variables should work without any difference between then (PTS_NPROC just being our custom one and NUMBER_OF_PROCESSORS checked anyhow as a fallback since that is exported on Windows).

[Michael]

Quick follow-up... To PTS Git (8.4.1 next week) I did add support for NUM_CPU_CORES similar to PTS_NPROC / NUMBER_OF_PROCESSORS, so moving forward for those that naturally expected to be able to use that env var for overriding the count can do so.

https://github.com/phoronix-test-suite/phoronix-test-suite/commit/ef35e7f06ec858e0840c1b7a6b6934defc66abfd

[JohnNeil]

Thanks for the quick follow up. I'm not seeing $NUMBER_OF_PROCESSORS or $PTS_NPROC affect the core count in the compress-7zip benchmark I am testing in PTS 8.4.0:

$ NUMBER_OF_PROCESSORS=1 phoronix-test-suite benchmark compress-7zip
...
Core Count: 4

Do tests have to have explicit support for these env vars for this to work to control the number of parallel threads?

[Michael]

Thanks for the quick follow up. I'm not seeing $NUMBER_OF_PROCESSORS or $PTS_NPROC affect the core count in the compress-7zip benchmark I am testing in PTS 8.4.0:

$ NUMBER_OF_PROCESSORS=1 phoronix-test-suite benchmark compress-7zip
...
Core Count: 4

Do tests have to have explicit support for these env vars for this to work to control the number of parallel threads?

Have you tried other tests besides compress-7zip? Looking at the test profile source [https://openbenchmarking.org/innhold...bfb0fc1bea389] it isn't passing any NUM_CPU_CORES to PTS. Normally PTS will use any --threads/-T argument etc for explicitly passing NUM_CPU_CORES to the upstream program where relevant. When checking the 7za man page [https://linux.die.net/man/1/7za] I am not seeing any argument for passing the threads to use to the program. If there is some argument, happy to update compress-7zip to use the explicit NUM_CPU_CORES.

But yeah if you are able to try with a test profile that does use NUM_CPU_CORES to verify the workflow is working out for you, that would be great. Thanks.