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Subject: Re: [PATCH 0/5] Support metric group constraint
To:     Andi Kleen <ak@linux.intel.com>
Cc:     Jiri Olsa <jolsa@redhat.com>, acme@kernel.org, mingo@redhat.com,
        peterz@infradead.org, linux-kernel@vger.kernel.org,
        mark.rutland@arm.com, namhyung@kernel.org,
        ravi.bangoria@linux.ibm.com, yao.jin@linux.intel.com
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From:   "Liang, Kan" <kan.liang@linux.intel.com>
Message-ID: <616a4f00-dd1f-20b2-a228-3fa9d7391016@linux.intel.com>
Date:   Thu, 20 Feb 2020 14:25:03 -0500
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On 2/20/2020 11:43 AM, Andi Kleen wrote:
>> For other metric groups, even they have cycles, the issue should not be
>> triggered.
>> For example, if they have 4 or less events, the cycles can be scheduled to
>> GP counter instead.
>> If they have 6 or more events, the weak group will be reject anyway.
>> Perf tool will open it as non-group (standalone metrics).
> 
> Technically it can also happen for 9 events with Hyper Threading off or
> on Icelake (8 generic counters)
> 
> I didn't think we had any of those, but please double check.
> 

I checked all public metrics groups. Right, we don't have such metrics 
group with 8 GP events + 1 cycles.
We only need to add watchdog constraint for Page_Walks_Utilization for now.

Thanks,
Kan