Messages in this thread | | | Date | Sat, 27 Nov 2010 00:25:36 +0800 | Subject | Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu | From | Lin Ming <> |
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On Fri, Nov 26, 2010 at 7:41 PM, Stephane Eranian <eranian@google.com> wrote: > On Fri, Nov 26, 2010 at 12:36 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> 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. > > I think the one core-only approach will limit the spurious interrupt aspect. > In perfmon, that's how I had it setup. The first CPU where uncore is > accessed owns the uncore PMU for the socket, thus all interrupts are > routed there. What you are proposing is the same. Now you can chose > you hardcode which is the default core to handle this, or (better) you > use the first core that accesses uncore. > >> >> 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. >> > Agreed. >
Hi, all
Thanks for all the comments. I'm on travel Nov 27 to Nov 30.
I'll address the comments when I'm back.
Thanks, Lin Ming
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