Re: [V2 PATCH] perf parse-events: Specially handle uncore event alias in small groups

[Liang, Kan]

On 4/25/2018 10:59 AM, Jiri Olsa wrote:
> On Wed, Apr 25, 2018 at 10:42:27AM -0400, Liang, Kan wrote:
> > On 4/25/2018 10:23 AM, Jiri Olsa wrote:
> > > On Wed, Apr 25, 2018 at 06:50:18AM -0700, kan.liang@xxxxxxxxxxxxxxx wrote:
> > > > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> > > >
> > > > Perf stat doesn't count the uncore event aliases from the same uncore
> > > > block in a group, for example:
> > > >
> > > >     perf stat -e '{unc_m_cas_count.all,unc_m_clockticks}' -a -I 1000
> > > >     #           time             counts unit events
> > > >          1.000447342      <not counted>      unc_m_cas_count.all
> > > >          1.000447342      <not counted>      unc_m_clockticks
> > > >          2.000740654      <not counted>      unc_m_cas_count.all
> > > >          2.000740654      <not counted>      unc_m_clockticks
> > > >
> > > > The output is very misleading. It gives a wrong impression that the
> > > > uncore event doesn't work.
> > > >
> > > > An uncore block could be composed by several PMUs. An uncore event alias
> > > > is a joint name which means the same event runs on all PMUs of a block.
> > > > Perf doesn't support mixed events from different PMUs in the same group.
> > > > It is wrong to put uncore event aliases in a big group.
> > > >
> > > > The right way is to split the big group into multiple small groups which
> > > > only include the events from the same PMU.
> > > > Only uncore event aliases from the same uncore block should be specially
> > > > handled here. It doesn't make sense to mix the uncore events with other
> > > > uncore events from different blocks or even core events in a group.
> > > >
> > > > With the patch:
> > > >     #           time             counts unit events
> > > >        1.001557653            140,833      unc_m_cas_count.all
> > > >        1.001557653      1,330,231,332      unc_m_clockticks
> > > >        2.002709483             85,007      unc_m_cas_count.all
> > > >        2.002709483      1,429,494,563      unc_m_clockticks
> > >
> > > hum, I still can see the original behaviour even with the patch:
> >
> > That's because the data_reads and clockticks are from different uncore
> > blocks. The data_reads is a IMC event. The clockticks is a CBOX event.
> >
> > The patch only supports the events from the same uncore blocks in group.
>
> I see, found another example from same uncore blocks and it seems to work:
>    #  perf stat -e '{cas_count_read,cas_count_write}' -a -I 1000
>
> but I have it aborted on:
>    # ./perf stat -e '{cas_count_read,cas_count_write,cas_count_read}' -a -I 1000
>    perf: util/evsel.c:1483: get_group_fd: Assertion `!(!leader->fd)' failed.
>    Aborted (core dumped)

Yes, there is a bug if leader and member have the same event name.
I will fix it in V3. Thanks for the test.

Thanks,
Kan