Messages in this thread | | | Date | Thu, 04 Dec 2008 23:50:11 -0800 (PST) | Subject | Re: [patch 0/3] [Announcement] Performance Counters for Linux | From | David Miller <> |
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From: Ingo Molnar <mingo@elte.hu> Date: Fri, 5 Dec 2008 07:10:12 +0100
> * David Miller <davem@davemloft.net> wrote: > > > From: Thomas Gleixner <tglx@linutronix.de> > > Date: Thu, 04 Dec 2008 23:44:39 -0000 > > > > > - No interaction with ptrace: any task (with sufficient permissions) can > > > monitor other tasks, without having to stop that task. > > > > This isn't going to work. > > > > If you look at the things the perfmon libraries do, you do need to stop > > the task. > > > > Consider counter virtualization as the most direct example. [...] > > Note that counter virtualization is not offered in the perfmon3 patchset > that has been posted to lkml. (It is part of the much larger 'full' > perfmon patchset which has not been submitted for integration)
I know, it was yanked out to make a merge more likely.
> Relying on ptrace machinery can be considered one of the bigger design > mistakes of the permon3 patchset.
I totally disagree.
> We pointed that out in review, and now we demonstrate it via this > patchset that it can be done much cleaner and much simpler. (Please stay > tuned for -v2 if you want to see the proof of the pudding.)
I hope it will provide enough for full PAPI library support, otherwise it's useless for most of the world.
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