linux-kernel - Re: [RFC PATCH v3] perf cs-etm: Split Coresight decode by aux records

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Message-ID: <dcf7cbe3-2d97-bf99-7025-3f62e2f09be1@arm.com>
Date:   Tue, 1 Jun 2021 16:09:12 +0300
From:   James Clark <james.clark@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Coresight ML <coresight@...ts.linaro.org>,
        Leo Yan <leo.yan@...aro.org>, Al Grant <al.grant@....com>,
        branislav.rankov@....com, Denis Nikitin <denik@...omium.org>,
        "Suzuki K. Poulose" <suzuki.poulose@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Leach <mike.leach@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-perf-users@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3] perf cs-etm: Split Coresight decode by aux records



On 27/05/2021 18:37, Mathieu Poirier wrote:
> On Thu, 27 May 2021 at 07:46, James Clark <james.clark@....com> wrote:
>>
>>
>>
>> On 27/05/2021 13:42, James Clark wrote:
>>> Populate the auxtrace queues using AUX records rather than whole
>>> auxtrace buffers.
>>>
>> ...
>>> Snapshot mode still needs to be tested.
>>>
>>
>> Snapshot mode is also working, but needs the following patch applied to reverse aux_offset
>> from the end of the buffer to the beginning:
> 
> It might be better to send another revision with this patch included
> in to make sure everyone is looking at (and testing) the same thing.

I've sent v4 with it applied. There was actually a mistake which broke the normal mode,
so it was a good idea to apply it.

> 
>>
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 5d6c03488187..9db556e14dfa 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -2700,6 +2700,7 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session,
>>         struct perf_record_auxtrace *auxtrace_event;
>>         union perf_event auxtrace_fragment;
>>         bool matchesCpuPid;
>> +       __u64 aux_offset;
>>         struct cs_etm_auxtrace *etm = container_of(session->auxtrace,
>>                                                    struct cs_etm_auxtrace,
>>                                                    auxtrace);
>> @@ -2730,19 +2731,26 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session,
>>         else
>>                 matchesCpuPid = auxtrace_event->cpu == sample->cpu;
>>
>> +       /*
>> +        * In snapshot/overwrite mode, the head points to the end of the buffer so aux_offset needs
>> +        * to have the size subtracted so it points to the beginning as in normal mode.
>> +        */
>> +       if (aux_event->flags && PERF_AUX_FLAG_OVERWRITE)
>> +               aux_offset = aux_event->aux_offset - aux_event->aux_size;
>> +       else
>> +               aux_offset = aux_event->aux_offset;
>> +
>>         if (matchesCpuPid &&
>> -           aux_event->aux_offset >= auxtrace_event->offset &&
>> -           aux_event->aux_offset + aux_event->aux_size <=
>> -                       auxtrace_event->offset + auxtrace_event->size) {
>> +           aux_offset >= auxtrace_event->offset &&
>> +           aux_offset + aux_event->aux_size <= auxtrace_event->offset + auxtrace_event->size) {
>>                 /*
>>                  * If this AUX event was inside this buffer somewhere, create a new auxtrace event
>>                  * based on the sizes of the aux event, and queue that fragment.
>>                  */
>>                 auxtrace_fragment.auxtrace = *auxtrace_event;
>>                 auxtrace_fragment.auxtrace.size = aux_event->aux_size;
>> -               auxtrace_fragment.auxtrace.offset = aux_event->aux_offset;
>> -               file_offset += aux_event->aux_offset - auxtrace_event->offset +
>> -                               auxtrace_event->header.size;
>> +               auxtrace_fragment.auxtrace.offset = aux_offset;
>> +               file_offset += aux_offset - auxtrace_event->offset + auxtrace_event->header.size;
>>                 return auxtrace_queues__add_event(&etm->queues,
>>                                                session,
>>                                                &auxtrace_fragment,
>>
>>