Messages in this thread | | | Subject | Re: [RFC PATCH] perf_core: provide a kernel-internal interface to get to performance counters | From | Peter Zijlstra <> | Date | Mon, 05 Oct 2009 09:53:30 +0200 |
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On Thu, 2009-10-01 at 10:53 +0200, Ingo Molnar wrote: > i'd suggest you extend perf events with a 'system > wide' event abstraction, which: > > - Enumerates such registered events (via a list) > > - Adds a CPU hotplug handler (which clones those events over to a new > CPU and directs it back to the ring-buffer of the existing event(s) > [if any]) > > - Plus a state field that allows the filtering out of stray/premature > events. > > Such an add-on layer/abstraction would sure be useful in other cases as > well. It might make sense to expose it to user-space and make perf top > use it by default.
Non-trivial.
Something like this would imply a single output channel for all these CPUs, and we've already seen that stuffing too many CPUs down one such channel (using -M) leads to significant performance issues.
Therefore I would strongly argue to let the kernel interface be what it is and solve this in a userspace library for those who care.
We really cannot sanely support an all-CPUs abstraction without running into trouble.
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