linux-kernel - Re: [PATCH 30/48] perf record: Generate tracking events for process forked by perf

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Date:	Wed, 24 Feb 2016 16:01:38 +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 30/48] perf record: Generate tracking events for process
 forked by perf

On Mon, Feb 22, 2016 at 09:10:57AM +0000, Wang Nan wrote:
> With 'perf record --switch-output' without -a, record__synthesize() in
> record__switch_output() won't generate tracking events because there's
> no thread_map in evlist. Which causes newly created perf.data doesn't
> contain map and comm information.
> 
> This patch creates a fake thread_map and directly call
> perf_event__synthesize_thread_map() for those events.
> 
> 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 | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 3a11102..7d4d8bf 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -567,6 +567,23 @@ record__switch_output(struct record *rec, bool at_exit)
>  		perf_session__create_kernel_maps(rec->session);
>  		perf_session__set_id_hdr_size(rec->session);
>  		record__synthesize(rec);
> +

could you please comment from changelog in here

> +		if (target__none(&rec->opts.target)) {

also this would be better in separate function:

> +			struct {
> +				struct thread_map map;
> +				struct thread_map_data map_data;
> +			} thread_map;
> +
> +			thread_map.map.nr = 1;
> +			thread_map.map.map[0].pid = rec->evlist->workload.pid;
> +			thread_map.map.map[0].comm = NULL;
> +			perf_event__synthesize_thread_map(&rec->tool,
> +					&thread_map.map,
> +					process_synthesized_event,
> +					&rec->session->machines.host,
> +					rec->opts.sample_address,
> +					rec->opts.proc_map_timeout);
> +		}
>  	}
>  	return fd;
>  }
> -- 
> 1.8.3.4
>