linux-kernel - Re: [PATCH 02/25] perf stat record: Add record command

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Date:	Fri, 6 Nov 2015 09:24:00 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Liang, Kan" <kan.liang@...el.com>
Subject: Re: [PATCH 02/25] perf stat record: Add record command

On Thu, Nov 05, 2015 at 05:51:01PM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

> In the second case it almost works, modulo that warning.
> 
> I think that what we need to achieve is for older tools to be able to, with a
> file produced by 'perf stat record', to show this:
> 
> [root@zoo ~]# perf report --no-header --stdio
> Error:
> The perf.data file has no samples!
> # To display the perf.data header info, please use --header/--header-only options.
> #
> [root@zoo ~]# 
> 
> 
> I.e. the file should look like one that is produced by this command, purposely
> to not create any sample:
> 
> # perf record -e syscalls:sys_enter_accept usleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.018 MB perf.data ]
> 
> 
> I applied the first patch and added it to that perf/stat branch.

well.. it's either simple patches and step by step
functionality or one big with everything..

[PATCH 02/25] perf stat record: Add record command
   - adds record command that creates empty perf.data

[PATCH 03/25] perf stat record: Initialize record features
   - adds FEATURES initialization for stat data

[PATCH 04/25] perf stat record: Synthesize stat record data
   - adds meta data

[PATCH 05/25] perf stat record: Store events IDs in perf data file
   - adds event IDs
...


you get proper warning right after patch 3/25, where
we store STAT feature bit and properly check it when
opening perf.data

I can merge patch 2 and 3 to get the proper warning
from begining.. but that'd be bigger patch ;-)

thanks,
jirka
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