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Date: Thu, 14 Apr 2016 20:59:13 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Wang Nan <wangnan0@huawei.com>
Cc: linux-kernel@vger.kernel.org, pi3orama@163.com,
        He Kuang <hekuang@huawei.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>, Jiri Olsa <jolsa@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Namhyung Kim <namhyung@kernel.org>, Zefan Li <lizefan@huawei.com>
Subject: Re: [PATCH v2 2/6] perf record: Split output into multiple files via
 '--switch-output'
Message-ID: <20160414235913.GK9056@kernel.org>
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Em Thu, Apr 14, 2016 at 02:22:01PM +0000, Wang Nan escreveu:
> Allow 'perf record' splits its output into multiple files.
> 
> For example:
> 
>  # ~/perf record -a --timestamp-filename --switch-output &
>  [1] 10763
>  # kill -s SIGUSR2 10763
>  [ perf record: dump data: Woken up 1 times ]
>  # [ perf record: Dump perf.data.2015122622314468 ]
> 
>  # kill -s SIGUSR2 10763
>  [ perf record: dump data: Woken up 1 times ]
>  # [ perf record: Dump perf.data.2015122622314762 ]
> 
>  # kill -s SIGUSR2 10763
>  [ perf record: dump data: Woken up 1 times ]
>  #[ perf record: Dump perf.data.2015122622315171 ]
> 
>  # fg
>  perf record -a --timestamp-filename --switch-output
>  ^C[ perf record: Woken up 1 times to write data ]
>  [ perf record: Dump perf.data.2015122622315513 ]
>  [ perf record: Captured and wrote 0.014 MB perf.data.<timestamp> (296 samples) ]

Added this as an initial man page entry:


diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 19aa17532a16..a77a431ca4ef 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -347,6 +347,14 @@ Configure all used events to run in kernel space.
 --all-user::
 Configure all used events to run in user space.
 
+--switch-output::
+Generate multiple perf.data files, timestamp prefixed, switching to a new one
+when receiving a SIGUSR2.
+
+A possible use case is to, given an external event, slice the perf.data file
+that gets then processed, possibly via a perf script, to decide if that
+particular perf.data snapshot should be kept or not.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]