linux-kernel - Re: [PATCH 29/48] perf record: Re-synthesize tracking events after output switching

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Date:	Wed, 24 Feb 2016 15:57:10 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	Alexei Starovoitov <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <dev@...yps.com>,
	"David S. Miller" <davem@...emloft.net>,
	He Kuang <hekuang@...wei.com>,
	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>, Jiri Olsa <jolsa@...nel.org>,
	Kirill Smelkov <kirr@...edi.com>,
	Li Zefan <lizefan@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, pi3orama@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 29/48] perf record: Re-synthesize tracking events after
 output switching

On Mon, Feb 22, 2016 at 09:10:56AM +0000, Wang Nan wrote:
> Tracking events describe kernel and threads. They are generated by
> reading /proc/kallsyms, /proc/*/maps and /proc/*/task/* during
> initialization of 'perf record', serialized into event sequences and put
> at the head of 'perf.data'. In case of output switching, each output
> file should contain those events.
> 
> This patch calls record__synthesize() during output switching, so the
> event sequences described above can be collected again.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Signed-off-by: He Kuang <hekuang@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
>  tools/perf/builtin-record.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 2839715..3a11102 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -529,6 +529,8 @@ record__finish_output(struct record *rec)
>  	return;
>  }
>  
> +static int record__synthesize(struct record *rec);
> +
>  static int
>  record__switch_output(struct record *rec, bool at_exit)
>  {
> @@ -557,6 +559,15 @@ record__switch_output(struct record *rec, bool at_exit)
>  	if (!quiet)
>  		fprintf(stderr, "[ perf record: Dump %s.%s ]\n",
>  			file->path, timestamp);
> +
> +	/* Reinit machine */
> +	if (!at_exit) {
> +		machines__exit(&rec->session->machines);
> +		machines__init(&rec->session->machines);
> +		perf_session__create_kernel_maps(rec->session);
> +		perf_session__set_id_hdr_size(rec->session);

hum, what's the reason to reinit machines data, it's still the same no?

I'd think that onlt record__synthesize call is needed in here

also I think we should introduce some perf_session helper
for that.. like perf_session__init or such

thanks,
jirka

> +		record__synthesize(rec);
> +	}
>  	return fd;
>  }
>  
> -- 
> 1.8.3.4
>