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 11:28:22 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.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 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@...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)
> 

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