lkml.org 
[lkml]   [2010]   [Nov]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu
    From
    Date
    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..


    \
     
     \ /
      Last update: 2010-11-25 07:11    [W:0.027 / U:59.820 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site