Re: disabling group leader perf_event

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 On 09/06/2010 02:24 PM, Peter Zijlstra wrote:
On Mon, 2010-09-06 at 12:12 +0300, Avi Kivity wrote:
If I read the code correctly, disabling a group leader perf_event will
disable the entire group.

Is this correct?
Yeah, pretty much.

Well, I never liked group_leader style APIs. I like different types for the container and the contained. But such is not unix.

If so, how can I disable just the event itself?  Can I allocate a dummy
invent for the group leader so I can enable and disable each perf_event
in the group individually?
Which makes me wonder why you use groups in the first place.

Basically, to read() all events in one go.  I have many of them.

My current problem is that I have an event (kvm_exit) which I want to drill down by looking at a field (exit_reason). So I create lots of separate perf_events with a filter for each reason: kvm_exit(exit_reason==0), kvm_exit(exit_reason==1), etc. But filters are fairly slow (can have ~60 such events on AMD), so I want to make this drill-down optional.

Current plan is to have a group for the basic events and another group for the drilldown events (each per-cpu), and activate the drilldown group on user request. perf will be able to schedule both groups concurrently since they only contain tracepoints, yes?

--
error compiling committee.c: too many arguments to function

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