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    SubjectRe: [RFC][PATCH v2 06/11] perf: core, export pmus via sysfs
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    On Wed, 2010-05-19 at 04:05 +0800, Greg KH wrote:
    > On Wed, May 19, 2010 at 01:46:42AM +0000, Lin Ming wrote:
    > > Now only exports cpu hardware events.
    > >
    > > For each PMU, there are 2 sysfs dirs: event_source and events.
    > >
    > > For example,
    > > /sys/devices/system/cpu/event_source/
    > > /sys/devices/system/cpu/events/
    > >
    > > $ tree /sys/devices/system/cpu/event_source/
    > > /sys/devices/system/cpu/event_source/
    > > `-- id
    > >
    > > $ tree /sys/devices/system/cpu/events/
    > > /sys/devices/system/cpu/events/
    > > |-- L1-dcache-load-misses
    > > | |-- event_source -> ../../event_source
    >
    > What is this symlink for? Is it needed as they all seem to point to the
    > same thing.

    The symlink is used to find the "event_source" of the "event".

    /sys/devices/system/cpu/event_source/

    /sys/devices/system/cpu/events/
    |-- L1-dcache-load-misses
    | |-- event_source -> ../../event_source

    For above example, "event_source" is the cpu pmu and the "event" is
    L1-dcache-load-misses.

    Yes, they point to the same thing, because all the events
    under /sys/devices/system/cpu/events/* is monitored by the same event
    source, ie, the cpu pmu(/sys/devices/system/cpu/event_source/).

    >
    > Also, as you are trying to add new sysfs interfaces, please document
    > them in Documentation/ABI.

    Will add the document.

    >
    > And, do you have to use "raw" kobjects here? Any chance you can use a
    > struct device instead?

    Let me think about this.

    >
    > I'm still not really understanding what exactly you are trying to show
    > in the sysfs tree here anyway, perhaps the documentation update will
    > clear that up for me.

    To support multiple pmus(or call them event source), I want to show all
    the pmus and events in the sysfs tree.

    For cpu pmu,
    /sys/devices/system/cpu/event_source/*
    /sys/devices/system/cpu/events/*

    For node pmu,
    /sys/devices/system/node/event_source/*
    /sys/devices/system/node/events/*

    For mce,
    /sys/kernel/events/mce/*

    and so on...the exact placement is not yet final.

    Thanks,
    Lin Ming

    >
    > thanks,
    >
    > greg k-h



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