Messages in this thread | | | Subject | Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu | From | Lin Ming <> | Date | Wed, 01 Dec 2010 11:28:43 +0800 |
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On Fri, 2010-11-26 at 19:36 +0800, Peter Zijlstra wrote: > On Fri, 2010-11-26 at 12:25 +0100, Stephane Eranian wrote: > > On Fri, Nov 26, 2010 at 12:24 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > > On Fri, 2010-11-26 at 09:18 +0100, Stephane Eranian wrote: > > > > > >> In the perf_event model, given that any one of the 4 cores can be used > > >> to program uncore events, you have no choice but to broadcast to all > > >> 4 cores. Each has to demultiplex and figure out which of its counters > > >> have overflowed. > > > > > > Not really, you can redirect all these events to the first online cpu of > > > the node. > > > > > > You can re-write event->cpu in pmu::event_init(), and register cpu > > > hotplug notifiers to migrate the state around. > > > > > I am sure you could. But then the user thinks the event is controlled > > from CPUx when it's actually from CPUz. I am sure it can work but > > that's confusing, especially interrupt-wise. > > Well, its either that or keeping a node wide state like we do for AMD > and serialize everything from there. > > And I'm not sure what's most expensive, steering the interrupt to one > core only, or broadcasting every interrupt, I'd favour the first > approach. > > The whole thing is a node-wide resource, so the user needs to think in > nodes anyway, we already do a cpu->node mapping for identifying the > thing.
How about a new sub-command for node-wide events statistics?
perf node -n <node> -e <event>?
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