[PATCH v4 2/6] perf record: Split output into multiple files via '--switch-output'

[Wang Nan]

Allow 'perf record' to split 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) ]

  # ls -l
  total 920
  -rw------- 1 root root 797692 Dec 26 22:31 perf.data.2015122622314468
  -rw------- 1 root root  59960 Dec 26 22:31 perf.data.2015122622314762
  -rw------- 1 root root  59912 Dec 26 22:31 perf.data.2015122622315171
  -rw------- 1 root root  19220 Dec 26 22:31 perf.data.2015122622315513

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
Link: http://lkml.kernel.org/r/1460643725-167413-3-git-send-email-wangnan0@xxxxxxxxxx
Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
[ Added man page entry ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/Documentation/perf-record.txt |  8 ++++++
 tools/perf/builtin-record.c              | 44 +++++++++++++++++++++++++++-----
 2 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 19aa175..a77a431 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]
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 0ff2422..7fd0b2d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -58,6 +58,7 @@ struct record {
 	bool			no_buildid_cache_set;
 	bool			buildid_all;
 	bool			timestamp_filename;
+	bool			switch_output;
 	unsigned long long	samples;
 };
 
@@ -130,6 +131,8 @@ static volatile int child_finished;
 
 static DEFINE_TRIGGER(auxtrace_snapshot);
 
+static DEFINE_TRIGGER(switch_output);
+
 static void sig_handler(int sig)
 {
 	if (sig == SIGCHLD)
@@ -649,9 +652,12 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	signal(SIGINT, sig_handler);
 	signal(SIGTERM, sig_handler);
 
-	if (rec->opts.auxtrace_snapshot_mode) {
+	if (rec->opts.auxtrace_snapshot_mode || rec->switch_output) {
 		signal(SIGUSR2, snapshot_sig_handler);
-		auxtrace_snapshot_on();
+		if (rec->opts.auxtrace_snapshot_mode)
+			auxtrace_snapshot_on();
+		if (rec->switch_output)
+			switch_output_on();
 	} else {
 		signal(SIGUSR2, SIG_IGN);
 	}
@@ -781,11 +787,13 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	}
 
 	auxtrace_snapshot_ready();
+	switch_output_ready();
 	for (;;) {
 		unsigned long long hits = rec->samples;
 
 		if (record__mmap_read_all(rec) < 0) {
 			auxtrace_snapshot_error();
+			switch_output_error();
 			err = -1;
 			goto out_child;
 		}
@@ -801,6 +809,22 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			}
 		}
 
+		if (switch_output_is_toggled()) {
+			switch_output_ready();
+
+			if (!quiet)
+				fprintf(stderr, "[ perf record: dump data: Woken up %ld times ]\n",
+					waking);
+			waking = 0;
+			fd = record__switch_output(rec, false);
+			if (fd < 0) {
+				pr_err("Failed to switch to new file\n");
+				switch_output_error();
+				err = fd;
+				goto out_child;
+			}
+		}
+
 		if (hits == rec->samples) {
 			if (done || draining)
 				break;
@@ -829,6 +853,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 		}
 	}
 	auxtrace_snapshot_off();
+	switch_output_off();
 
 	if (forks && workload_exec_errno) {
 		char msg[STRERR_BUFSIZE];
@@ -1264,6 +1289,8 @@ struct option __record_options[] = {
 		    "Record build-id of all DSOs regardless of hits"),
 	OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
 		    "append timestamp to output filename"),
+	OPT_BOOLEAN(0, "switch-output", &record.switch_output,
+		    "Switch output when receive SIGUSR2"),
 	OPT_END()
 };
 
@@ -1412,9 +1439,12 @@ out_symbol_exit:
 
 static void snapshot_sig_handler(int sig __maybe_unused)
 {
-	if (!auxtrace_snapshot_is_ready())
-		return;
-	auxtrace_snapshot_toggle();
-	if (auxtrace_record__snapshot_start(record.itr))
-		auxtrace_snapshot_error();
+	if (auxtrace_snapshot_is_ready()) {
+		auxtrace_snapshot_toggle();
+		if (auxtrace_record__snapshot_start(record.itr))
+			auxtrace_snapshot_error();
+	}
+
+	if (switch_output_is_ready())
+		switch_output_toggle();
 }
-- 
1.8.3.4