> From: Tomasz Duszynski [mailto:tduszyn...@marvell.com]
> Sent: Thursday, 26 January 2023 16.28
>
> >From: Bruce Richardson <bruce.richard...@intel.com>
> >Sent: Thursday, January 26, 2023 1:59 PM
> >
> >Other possible complication is - how does this work with threads that
> are not pinned to a
> >particular physical core? Do things work as expected in that case?
> >
>
> It's assumed that once set of counters is enabled on particular l-core
> then this thread shouldn't be migrating
> back and for the obvious reasons.
>
> But, once scheduled elsewhere all should still work as expected.
Just to elaborate what Tomasz stated here...
The patch contains this line (code comments are mine):
return syscall(SYS_perf_event_open, &attr, /*pid*/ 0, /*cpu*/ -1, group_fd, 0);
And man 2 perf_event_open [1] says:
pid == 0 and cpu == -1:
This measures the calling process/thread on any CPU.
So it should work just fine, even when a thread is not pinned to a particular
physical core.
[1]: https://man7.org/linux/man-pages/man2/perf_event_open.2.html
