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

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Date:   Wed, 25 Apr 2018 16:59:20 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...nel.org, mingo@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, namhyung@...nel.org,
        ganapatrao.kulkarni@...ium.com, zhangshaokun@...ilicon.com,
        yao.jin@...ux.intel.com, will.deacon@....com, ak@...ux.intel.com,
        agustinv@...eaurora.org
Subject: Re: [V2 PATCH] perf parse-events: Specially handle uncore event
 alias in small groups

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@...ux.intel.com wrote:
> > > From: Kan Liang <kan.liang@...ux.intel.com>
> > > 
> > > 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)

jirka