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    SubjectRe: [PATCH v2 6/6] perf tool: Parse general/raw events from sysfs
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    On Sun, 2011-08-07 at 04:10 +0800, Stephane Eranian wrote:
    > Hi,
    >
    > On Fri, Jul 15, 2011 at 7:35 AM, Lin Ming <ming.m.lin@intel.com> wrote:
    > > PMU can export general events to sysfs, for example,
    > >
    > > /sys/bus/event_source/devices/uncore/events
    > > └── cycle
    > >
    > > Then specify the event as <pmu>:<event>,
    > >
    > > $ sudo perf stat -a -C 0 -e uncore:cycle
    >
    > I think this event syntax should be adjusted a bit.
    >
    > How would the tool differentiate:
    > perf stat -e uncore:cycle
    > form:
    > perf stat -e cycle:u
    >
    > It would have to scan sysfs for a 'cycle' PMU and conclude
    > there is none, then resolve the 'cycle' event name. And if
    > you're unlucky and you have a event name that matches
    > the PMU name, you get into troubles.
    >
    > I think, one could instead do:
    >
    > perf stat -e uncore::cycle:k
    >
    > That way, by virtue of the '::' separator, the tool would know
    > that it needs to first look into sysfs for an 'uncore' PMU, then
    > it needs to look for the 'cycle' event.

    Yes, I like this '::' separator too.
    Will update to use it.

    >
    > I also use the '::' notation in libpfm4 to separate the PMU model
    > form the event+umask+modifiers.
    >
    > I also suspect that with this sysfs interface for PMU models, you
    > would simply add a number to differentiate each instance of a PMU.
    > So for GPU, you would do:
    > perf stat -e gfx0::cycles
    >
    > Is that right?

    A number or other thing is OK.

    int perf_pmu_register(struct pmu *pmu, char *name, int type)
    will be called to register a PMU.

    So I think any name that can differentiate each instance is OK.

    Adding a number looks like the easiest way.

    Thanks,
    Lin Ming


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