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    SubjectRe: [RFC][PATCH 3/9] perf: export registerred pmus via sysfs
    On Tue, May 11, 2010 at 11:48:42AM +0200, Peter Zijlstra wrote:
    > On Tue, 2010-05-11 at 17:40 +0800, Lin Ming wrote:
    > > Is /sys/class/event_sources/* looks like,
    > >
    > > /sys/class/event_sources/cpu_hw_events0
    > > -> /sys/devices/system/cpu/cpu0/cpu_hw_events
    > > ...
    > > /sys/class/event_sources/cpu_hw_eventsN
    > > -> /sys/devices/system/cpu/cpuN/cpu_hw_events
    > >
    > > /sys/class/event_sources/cpu_hw_cache_events0
    > > -> /sys/devices/system/cpu/cpu0/cpu_hw_events
    > > ...
    > > /sys/class/event_sources/cpu_hw_cache_eventsN
    > > -> /sys/devices/system/cpu/cpuN/cpu_hw_events
    >
    > Hmm, good question.
    >
    > No all the cpus would have the same event sources. I'm not sure if we
    > can make sysfs understand that though (added GregKH and Kay to CC).
    >
    This is something I've been thinking about, too. On SH we have a
    large set of perf counter events that are entirely dependent on the
    configuration of the CPU they're on, with no requirement that these
    configurations are identical on all CPUs in an SMP configuration.

    As an example, it's possible to halve the L1 dcache and use that part of
    it as a small and fast memory which has completely different events
    associated with it from the regular L1 dcache events. These events would
    be invalid on a CPU that was running with all cache ways enabled but
    might also be valid on other CPUs that bolt these events to an extra SRAM
    outside of the cache topology completely.

    In any event, the events are at least consistent across all CPUs, it's
    only which ones are valid on a given CPU at a given time that can change.


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