linux-kernel - Re: [PATCH V6 09/14] perf/x86/intel: Support TopDown metrics on Ice Lake

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Message-ID: <59795cbd-a95c-8fdd-522d-199fbb047b8a@linux.intel.com>
Date:   Tue, 21 Jul 2020 11:50:49 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     peterz@...radead.org
Cc:     acme@...hat.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
        jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V6 09/14] perf/x86/intel: Support TopDown metrics on Ice
 Lake



On 7/21/2020 10:31 AM, peterz@...radead.org wrote:
> On Tue, Jul 21, 2020 at 10:23:36AM -0400, Liang, Kan wrote:
> 
>> Patch 13 forces the slots event to be part of a metric group. In patch 7,
>> for a metric group, we only update the values once with slots event.
>> I think the normal case mentioned above should not happen.
>>
>> +	/* Only need to call update_topdown_event() once for group read. */
>> +	if ((cpuc->txn_flags & PERF_PMU_TXN_READ) &&
>> +	    !is_slots_event(event))
>> +		return;
>> +
>> +	perf_pmu_disable(event->pmu);
>> +	x86_pmu.update_topdown_event(event);
>> +	perf_pmu_enable(event->pmu);
> 
> Ah, I missed that.
> 
> That also requires SLOTS to be the leader so that it will be the first
> read. Did we enforce that somewhere?

I think it's missed in the current patch set. The suggested code in 
patch 11 forces SLOTS to be the leader. I will apply it in V7.

Thanks,
Kan