linux-kernel - Re: [PATCH] perf tools: Exit recording if events have non matching sample type

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Date:	Thu, 29 Sep 2011 20:06:13 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, a.p.zijlstra@...llo.nl,
	mingo@...e.hu, paulus@...ba.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tools: Exit recording if events have non matching
	sample type

Em Thu, Sep 29, 2011 at 04:55:23PM -0600, David Ahern escreveu:
> On 09/29/2011 04:05 PM, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Sep 29, 2011 at 06:01:08PM +0200, Jiri Olsa escreveu:
> >> Following command hangs on my setup:
> >>   ./perf record -o perf.data -e ext4:ext4_mb_new_group_pa \
> >>    -e LLC-loads -- date '+%F'
> >>
> >> because hardware and tracepoint events have different sample type.
> >>
> >> With the patch applied the record command displays
> >> "Non matching sample_type" message and exits.
> > 
> > That is way too cryptic :-\
> > 
> > What is that makes the sample type not match in this case? Can we make
> > it match instead?
> > 
> > This is something to be properly fixed by _allowing_ non matching sample
> > types, the evsel/evlist abstractions are getting we close but not there
> > yet, multiple files in a perf.data/ directory are needed.
> 
> >From what I can see sample_type has to be the same for all samples:
> https://lkml.org/lkml/2011/8/15/6

We could add a PERF_SAMPLE_ID2 that if present would be guaranteed to be
the last, or we can, as PeterZ prefers/suggests, to use one mmap per
sample id, then we know that if we're getting it on that mmap, it has
that sample_type.

For record that means we need to dump each per-sample_id mmap onto a
separate file, i.e. use a directory, etc.

But what I suggested as a short term solution was to check what is the
difference in the above case and then make them use a single sample
type, i.e. bow to the current restriction.

- Arnaldo

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