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

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Message-ID: <YJBIRoRZ9WKvELQc@kernel.org>
Date:   Mon, 3 May 2021 16:00:22 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf record: Set timestamp boundary for AUX area events

Em Mon, May 03, 2021 at 09:11:31AM -0700, Andi Kleen escreveu:
> On Mon, May 03, 2021 at 06:06:38PM +0300, Adrian Hunter wrote:
> > 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
> 
> Ok makes sense.
> 
> Acked-by: Andi Kleen <ak@...ux.intel.com>

Thanks, applied.

- Arnaldo