linux-kernel - Re: [tip:perf/urgent] perf/x86/cqm: Fix CQM handling of grouping events into a cache

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Date:	Mon, 21 Mar 2016 11:14:37 -0700 (PDT)
From:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:	Matt Fleming <matt@...eblueprint.co.uk>
cc:	hpa@...or.com, eranian@...gle.com, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, brgerst@...il.com, peterz@...radead.org,
	bp@...en8.de, tglx@...utronix.de, vikas.shivappa@...ux.intel.com,
	dsahern@...il.com, dvlasenk@...hat.com, jolsa@...hat.com,
	luto@...capital.net, mingo@...nel.org, acme@...hat.com,
	torvalds@...ux-foundation.org, namhyung@...nel.org,
	vincent.weaver@...ne.edu, alexander.shishkin@...ux.intel.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf/x86/cqm: Fix CQM handling of grouping
 events into a cache_group



On Mon, 21 Mar 2016, Matt Fleming wrote:

> On Mon, 21 Mar, at 02:51:29AM, tip-bot for Vikas Shivappa wrote:
>> Commit-ID:  a223c1c7ab4cc64537dc4b911f760d851683768a
>> Gitweb:     http://git.kernel.org/tip/a223c1c7ab4cc64537dc4b911f760d851683768a
>> Author:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>
>> AuthorDate: Thu, 10 Mar 2016 15:32:07 -0800
>> Committer:  Ingo Molnar <mingo@...nel.org>
>> CommitDate: Mon, 21 Mar 2016 09:08:18 +0100
>>
>> perf/x86/cqm: Fix CQM handling of grouping events into a cache_group
>>
>> Currently CQM (cache quality of service monitoring) is grouping all
>> events belonging to same PID to use one RMID. However its not counting
>> all of these different events. Hence we end up with a count of zero
>> for all events other than the group leader.
>
> The reason that was done originally was because reporting for all events
> in a group led to duplicate values, since you'd be emitting the same
> RMID value multiple times.
>
> Is this no longer a problem?

Before MBM , the below condition was never hit because we had only one event ?

-       if (a->hw.target == b->hw.target)
+       if (a->hw.target == b->hw.target) {
+               b->hw.is_group_event = true;

We are trying to address this for cases where different MBM(local or total) and 
cqm events are grouped into one RMID.

Which is the case which led to duplicate values ?

Thanks,
Vikas

>