linux-kernel - Re: [PATCH] perf record: Set timestamp boundary for AUX area events

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Date:   Mon, 3 May 2021 18:06:38 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf record: Set timestamp boundary for AUX area events

On 3/05/21 5:56 pm, Andi Kleen wrote:
> On Mon, May 03, 2021 at 09:42:22AM +0300, Adrian Hunter wrote:
>> AUX area data is not processed by 'perf record' and consequently the
>>  --timestamp-boundary option may result in no values for "time of first
>> sample" and "time of last sample". However there are non-sample events
>> that can be used instead, namely 'itrace_start' and 'aux'.

"instead" -> "as well"

>> 'itrace_start' is issued before tracing starts, and 'aux' is issued
>> every time data is ready.
> 
> Hmm, what happens when some other non PT events are in the same perf record?

The sample timestamps are still processed, so the lowest sample timestamp or
'itrace_start' timestamp or 'aux' timestamp is the start.  Similarly for the end.

> And those maybe run at different times than PT (e.g. due to some PT specific
> filter).  Does this all work correctly then?

The broadest range is used