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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 18:26 +0800, Lin Ming wrote:

    > > 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?

    No, because as I said, then its ambiguous what pmu you want. If you have
    that, you need to extend your topology information.

    Anyway, I talked with Ingo on this and he'd like to see this somewhat
    extended.

    Instead of a pmu_id field, which we pass into a new
    perf_event_attr::pmu_id field, how about creating an event_source sysfs
    class. Then each class can have an event_source_id and a hierarchy of
    'generic' events.

    We'd start using the PERF_TYPE_ space for this and express the
    PERF_COUNT_ space in the event attributes found inside that class.

    That way we can include all the existing event enumerations into this as
    well.

    This way we can create:

    /sys/devices/system/cpu/cpuN/cpu_hardware_events
    cpu_hardware_events/event_source_id
    cpu_hardware_events/cpu_cycles
    cpu_hardware_events/instructions
    /...

    /sys/devices/system/cpu/cpuN/cpu_raw_events
    cpu_raw_events/event_source_id


    These would match the current PERF_TYPE_* values for compatibility

    For new PMUs we can start a dynamic range of PERF_TYPE_ (say at 64k but
    that's not ABI and can be changed at any time, we've got u32 to play
    with).

    For uncore this would result in:

    /sys/devices/system/node/nodeN/node_raw_events
    node_raw_events/event_source_id

    and maybe:

    /sys/devices/system/node/nodeN/node_events
    node_events/event_source_id
    node_events/local_misses
    /local_hits
    /remote_misses
    /remote_hits
    /...


    The software events and tracepoints and kprobes stuff we could hang off
    of /sys/kernel/ or something

    So your registration would indeed look like something:

    perf_event_register_pmu(struct pmu *pmu, int type),

    where type would normally be -1 (dynamic) but would be PERF_TYPE_ for
    those already laid down in ABI.

    This approach will also give us a good overview
    in /sys/class/event_source/, which will be a flat listing of all
    existing event sources.

    Does this make sense?




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