Re: [PATCH 04/13] perf/x86/amd: Support PERF_SAMPLE_WEIGHT using IBS OP_DATA3[IbsDcMissLat]

From: Ravi Bangoria <ravi.bangoria@amd.com>
To: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org, acme@kernel.org, jolsa@kernel.org,
	namhyung@kernel.org, irogers@google.com, jmario@redhat.com,
	leo.yan@linaro.org, alisaidi@amazon.com, ak@linux.intel.com,
	kan.liang@linux.intel.com, dave.hansen@linux.intel.com,
	hpa@zytor.com, mingo@redhat.com, mark.rutland@arm.com,
	alexander.shishkin@linux.intel.com, tglx@linutronix.de,
	bp@alien8.de, x86@kernel.org, linux-perf-users@vger.kernel.org,
	linux-kernel@vger.kernel.org, sandipan.das@amd.com,
	ananth.narayan@amd.com, kim.phillips@amd.com,
	santosh.shukla@amd.com, Ravi Bangoria <ravi.bangoria@amd.com>
Subject: Re: [PATCH 04/13] perf/x86/amd: Support PERF_SAMPLE_WEIGHT using IBS OP_DATA3[IbsDcMissLat]
Date: Thu, 26 May 2022 17:44:54 +0530	[thread overview]
Message-ID: <8b124340-a89b-bd7a-240c-c7f58fffd877@amd.com> (raw)
In-Reply-To: <CABPqkBQ-4vpG_d-u-Q-pTQ_wDg_HhqNNC3dSLFE6MS5Bp3qTDw@mail.gmail.com>

On 25-May-22 6:28 PM, Stephane Eranian wrote:
> On Wed, May 25, 2022 at 12:42 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
>>
>> IBS Op data3 provides data cache miss latency which can be passed as
>> sample->weight along with perf_mem_data_src. Note that sample->weight
>> will be populated only when PERF_SAMPLE_DATA_SRC is also set, although
>> both sample types are independent.
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
>> ---
>>  arch/x86/events/amd/ibs.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
>> index 6626caeed6a1..5a6e278713f4 100644
>> --- a/arch/x86/events/amd/ibs.c
>> +++ b/arch/x86/events/amd/ibs.c
>> @@ -738,6 +738,12 @@ static void perf_ibs_get_mem_lvl(struct perf_event *event, u64 op_data2,
>>                 return;
>>         }
>>
>> +       /* Load latency (Data cache miss latency) */
>> +       if (data_src->mem_op == PERF_MEM_OP_LOAD &&
>> +           event->attr.sample_type & PERF_SAMPLE_WEIGHT) {
>> +               data->weight.full = (op_data3 & IBS_DC_MISS_LAT_MASK) >> IBS_DC_MISS_LAT_SHIFT;
>> +       }
>> +
> I think here you also need to handle the WEIGHT_STRUCT case and put
> the cache miss latency in the right
> field. This IBS field covers the cache line movement and not the whole
> instruction latency which is the tag to ret field.
> In the case of WEIGHT_STRUCT you need to fill out the two fields.

Yeah, will do. Thanks for pointing it.

-Ravi