linux-kernel - Re: [RFC 02/11] perf/core: Data structure to present hazard data

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Message-Id: <c9dc6d62-3847-4080-8122-d62621455372@linux.ibm.com>
Date:   Mon, 2 Mar 2020 19:53:26 +0530
From:   maddy <maddy@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com, mpe@...erman.id.au, paulus@...ba.org,
        mingo@...hat.com, acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, adrian.hunter@...el.com, ak@...ux.intel.com,
        kan.liang@...ux.intel.com, alexey.budankov@...ux.intel.com,
        yao.jin@...ux.intel.com, robert.richter@....com,
        kim.phillips@....com,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Subject: Re: [RFC 02/11] perf/core: Data structure to present hazard data



On 3/2/20 3:25 PM, Peter Zijlstra wrote:
> On Mon, Mar 02, 2020 at 10:53:46AM +0530, Ravi Bangoria wrote:
>> From: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
>>
>> Introduce new perf sample_type PERF_SAMPLE_PIPELINE_HAZ to request kernel
>> to provide cpu pipeline hazard data. Also, introduce arch independent
>> structure 'perf_pipeline_haz_data' to pass hazard data to userspace. This
>> is generic structure and arch specific data needs to be converted to this
>> format.
>>
>> Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
>> ---
>>   include/linux/perf_event.h            |  7 ++++++
>>   include/uapi/linux/perf_event.h       | 32 ++++++++++++++++++++++++++-
>>   kernel/events/core.c                  |  6 +++++
>>   tools/include/uapi/linux/perf_event.h | 32 ++++++++++++++++++++++++++-
>>   4 files changed, 75 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
>> index 547773f5894e..d5b606e3c57d 100644
>> --- a/include/linux/perf_event.h
>> +++ b/include/linux/perf_event.h
>> @@ -1001,6 +1001,7 @@ struct perf_sample_data {
>>   	u64				stack_user_size;
>>   
>>   	u64				phys_addr;
>> +	struct perf_pipeline_haz_data	pipeline_haz;
>>   } ____cacheline_aligned;
>>   
>>   /* default value for data source */
>> @@ -1021,6 +1022,12 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
>>   	data->weight = 0;
>>   	data->data_src.val = PERF_MEM_NA;
>>   	data->txn = 0;
>> +	data->pipeline_haz.itype = PERF_HAZ__ITYPE_NA;
>> +	data->pipeline_haz.icache = PERF_HAZ__ICACHE_NA;
>> +	data->pipeline_haz.hazard_stage = PERF_HAZ__PIPE_STAGE_NA;
>> +	data->pipeline_haz.hazard_reason = PERF_HAZ__HREASON_NA;
>> +	data->pipeline_haz.stall_stage = PERF_HAZ__PIPE_STAGE_NA;
>> +	data->pipeline_haz.stall_reason = PERF_HAZ__SREASON_NA;
>>   }
> NAK, Don't touch anything outside of the first cacheline here.

My bad, should have looked at the comment in "struct perf_sample_data {".
Will move it to perf_prepare_sample().

Thanks for comments.
Maddy