Messages in this thread | | | Date | Fri, 5 Dec 2008 20:34:09 +1100 | From | Paul Mackerras <> | Subject | Re: [patch 0/3] [Announcement] Performance Counters for Linux |
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Ingo Molnar writes:
> The 'target' task does not have to be stopped to offer counter > virtualization (counter overcommit or counter scheduling) - or to offer > any of the other performance counter features. Please let us know why it > needs the task to be stopped - we asked about that on lkml in the perfmon > thread and no technical answer was given, and couldnt find any such > technical reason while implementing it ourselves.
I like this feature of your patchset, in fact, and the code looks pretty clean (as I would expect :). What I don't like (as I have already said) is having to use an API that splits up the PMU into pieces, plus the requirement that flows from that to have the kernel know about the event selection logic on every CPU model we support.
One thing I haven't figured out yet is what happens if you have a counter on a task and the task dies. Can I still use the counter fd after the task has died, and read out the total count?
Paul.
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