Messages in this thread | | | Subject | Re: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu | From | Lin Ming <> | Date | Thu, 25 Nov 2010 14:27:53 +0800 |
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On Thu, 2010-11-25 at 14:09 +0800, Peter Zijlstra wrote: > On Thu, 2010-11-25 at 08:24 +0800, Lin Ming wrote: > > On Tue, 2010-11-23 at 18:00 +0800, Stephane Eranian wrote: > > > On Sun, Nov 21, 2010 at 6:44 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > > > On Sun, 2010-11-21 at 22:04 +0800, Lin Ming wrote: > > > >> On Sun, 2010-11-21 at 20:46 +0800, Andi Kleen wrote: > > > >> > > > > > >> > > 2. Uncore pmu NMI handling > > > >> > > > > > >> > > All the 4 cores are programmed to receive uncore counter overflow > > > >> > > interrupt. The NMI handler(running on 1 of the 4 cores) handle all > > > >> > > counters enabled by all 4 cores. > > > >> > > > > >> > Really for uncore monitoring there is no need to use an NMI handler. > > > >> > You can't profile a core anyways, so you can just delay the reporting > > > >> > a little bit. It may simplify the code to not use one here > > > >> > and just use an ordinary handler. > > > >> > > > >> OK, I can use on ordinary interrupt handler here. > > > > > > > > Does the hardware actually allow using a different interrupt source? > > > > > > > It does not. It's using whatever you've programmed into the APIC > > > LVT vector, AFAIK. Uncore interrupt mode is enabled via > > > IA32_DEBUGCTL. Regarless of sampling or not, you need the interrupt > > > to virtualize the counters to 64 bits. > > > > If only counting(perf stat) makes sense for uncore events, do we still > > need an interrupt handler? > > Yep, I see no reason to dis-allow sampling. Sure its hard to make sense > of it, but since there are people who offline all but one cpu of a > package, I bet there are people who will run just one task on a package > as well. > > Just because it doesn't make sense in general doesn't mean there isn't > anybody who'd want to do it and actually knows wth he's doing. > > > 48 bits counter is not that easy to overflow in practice. > > Still..
OK, will do more tests, then send out a new version.
Thanks.
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