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SubjectRe: [PATCH v2 1/6] perf: Add interface to add general events to sysfs
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On Tue, 2011-07-19 at 15:52 +0800, Lin Ming wrote:
> On Mon, 2011-07-18 at 21:34 +0800, Peter Zijlstra wrote:
> > On Fri, 2011-07-15 at 14:34 +0000, Lin Ming wrote:
> > > PMU can implement ::add_events() to add its general events to sysfs.
> > >
> > > For example,
> > >
> > > /sys/bus/event_source/devices/uncore/events
> > > └── cycle
> > >
> > > Signed-off-by: Lin Ming <ming.m.lin@intel.com>
> > > ---
> > > include/linux/perf_event.h | 9 +++++++
> > > kernel/events/core.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 61 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> > > index 3f2711c..14337a3 100644
> > > --- a/include/linux/perf_event.h
> > > +++ b/include/linux/perf_event.h
> > > @@ -676,6 +676,14 @@ struct pmu {
> > > * for each successful ->add() during the transaction.
> > > */
> > > void (*cancel_txn) (struct pmu *pmu); /* optional */
> > > +
> > > + void (*add_events) (void);
> > > +};
> >
> > I'd rather not have a function pointer here, and all the kobj thingies
> > can be hooking into the existing struct device, right?
>
> I forgot to mention one important reason why I added a function pointer.
>
> The events can only be added to sysfs after PMU sysfs is initialized in
> perf_event_sysfs_init ->
> pmu_dev_alloc
>
> > @@ -5571,6 +5571,8 @@ static int pmu_dev_alloc(struct pmu *pmu)
> > if (ret)
> > goto free_dev;
> >
> > + if (pmu->add_events)
> > + pmu->add_events();
>
> So we need a pmu callback which is called in pmu_dev_alloc to add events
> to sysfs.
>
> You suggested a new interface,
> int perf_pmu_add_event(struct pmu *pmu, const char *name, u64 config)
>
> But where should it be called?
> I guess you mean to call it in pmu init function, for example,
> uncore_pmu_init.
>
> But pmu init function maybe called before perf_event_sysfs_init, which
> means the pmu sysfs has not been initialized yet.

Hi, Peter

Will you have a chance to look at this?

Thanks.

>
> Lin Ming


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