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    SubjectRe: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs
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    On Mon, 2010-05-10 at 18:35 +0800, Paul Mundt wrote:
    > On Mon, May 10, 2010 at 06:26:35PM +0800, Lin Ming wrote:
    > > On Mon, 2010-05-10 at 18:18 +0800, Peter Zijlstra wrote:
    > > > On Mon, 2010-05-10 at 18:11 +0800, Lin Ming wrote:
    > > > > On Mon, 2010-05-10 at 17:40 +0800, Peter Zijlstra wrote:
    > > > > > On Mon, 2010-05-10 at 17:27 +0800, Lin Ming wrote:
    > > > > > > Export pmus via sysfs /sys/devices/system/cpu/pmus/0...N
    > > > > > > The file name is the pmu id, ie, /sys/devices/system/cpu/pmus/N
    > > > > > > represents pmu id N.
    > > > > > > So perf tool can use it to initialize perf_event_attr.
    > > > > >
    > > > > > Why create a whole new directory, why not:
    > > > > >
    > > > > > /sys/devices/system/cpu/cpuN/pmu_id ?
    > > > >
    > > > >
    > > > > Do you mean /sys/devices/system/cpu/cpuN/pmu_id contain all ids?
    > > > >
    > > > > For example, each cpu has 4 pmus and the file pmu_id shows something
    > > > > like,
    > > > >
    > > > > #cat /sys/devices/system/cpu/cpu0/pmu_id
    > > > > 0 1 2 3
    > > >
    > > > No, I'm assuming there is only 1 PMU per CPU. Corey is the expert on
    > > > crazy hardware though, but I think the sanest way is to extend the CPU
    > > > topology if there's more structure to it.
    > >
    > > But our goal is to support multiple pmus, don't we need to assume there
    > > are more than 1 PMU per CPU?
    > >
    > The multiple PMU case still suggests 1 per CPU in most (all?) cases. If
    > you're thinking of PMUs in the northbridge case this would sit under its
    > own topology given that most CPUs will have a shared view of it. Do you

    Take Nehalem core and uncore pmu as an example,

    core pmu sits under /sys/devices/system/cpu/cpuN/pmu_id with ID 0,

    But uncore pmu is shared by cpus within package, where should it sit
    under?

    > have some cases with performance counters in per-CPU memory controllers
    > or something similar?

    Not sure about this now. I'll check.

    >
    > > How about
    > > /sys/devices/system/cpu/cpuN/pmu_0
    > > /sys/devices/system/cpu/cpuN/pmu_1
    > > /sys/devices/system/cpu/cpuN/pmu_2
    > > /sys/devices/system/cpu/cpuN/pmu_3
    > > ....?
    > >
    > If you're following driver model naming conventions, then these should
    > all be pmu.0, pmu.1, etc, etc.

    Thanks,
    Lin Ming



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