perf record: Add switch-output size option argument

It's now possible to specify the threshold size for perf.data like:

  $ perf record --switch-output=2G ...

Once it's reached, the current data are dumped in to the
perf.data.<timestamp> file and session does on.

  $ perf record --switch-output=2G ...
  [ perf record: dump data: Woken up 7244 times ]
  [ perf record: Dump perf.data.2017010214093746 ]
  ...

The size is expected to be a number with appended unit character -
B/K/M/G.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1483955520-29063-5-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-record.txt

@@ -421,9 +421,17 @@ Configure all used events to run in user space.
 --timestamp-filename
 Append timestamp to output file name.
 
---switch-output::
+--switch-output[=mode]::
 Generate multiple perf.data files, timestamp prefixed, switching to a new one
-when receiving a SIGUSR2.
+based on 'mode' value:
+  "signal" - when receiving a SIGUSR2 (default value) or
+  <size>   - when reaching the size threshold, size is expected to
+             be a number with appended unit character - B/K/M/G
+
+             Note: the precision of  the size  threshold  hugely depends
+             on your configuration  - the number and size of  your  ring
+             buffers (-m). It is generally more precise for higher sizes
+             (like >5M), for lower values expect different sizes.
 
 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

tools/perf/builtin-record.c

@@ -47,7 +47,9 @@
 #include <linux/time64.h>
 
 struct switch_output {
+	bool		 enabled;
 	bool		 signal;
+	unsigned long	 size;
 	const char	*str;
 	bool		 set;
 };
@@ -72,6 +74,23 @@ struct record {
 	unsigned long long	samples;
 };
 
+static volatile int auxtrace_record__snapshot_started;
+static DEFINE_TRIGGER(auxtrace_snapshot_trigger);
+static DEFINE_TRIGGER(switch_output_trigger);
+
+static bool switch_output_signal(struct record *rec)
+{
+	return rec->switch_output.signal &&
+	       trigger_is_ready(&switch_output_trigger);
+}
+
+static bool switch_output_size(struct record *rec)
+{
+	return rec->switch_output.size &&
+	       trigger_is_ready(&switch_output_trigger) &&
+	       (rec->bytes_written >= rec->switch_output.size);
+}
+
 static int record__write(struct record *rec, void *bf, size_t size)
 {
 	if (perf_data_file__write(rec->session->file, bf, size) < 0) {
@@ -80,6 +99,10 @@ static int record__write(struct record *rec, void *bf, size_t size)
 	}
 
 	rec->bytes_written += size;
+
+	if (switch_output_size(rec))
+		trigger_hit(&switch_output_trigger);
+
 	return 0;
 }
 
@@ -199,10 +222,6 @@ static volatile int done;
 static volatile int signr = -1;
 static volatile int child_finished;
 
-static volatile int auxtrace_record__snapshot_started;
-static DEFINE_TRIGGER(auxtrace_snapshot_trigger);
-static DEFINE_TRIGGER(switch_output_trigger);
-
 static void sig_handler(int sig)
 {
 	if (sig == SIGCHLD)
@@ -848,11 +867,11 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	signal(SIGTERM, sig_handler);
 	signal(SIGSEGV, sigsegv_handler);
 
-	if (rec->opts.auxtrace_snapshot_mode || rec->switch_output.signal) {
+	if (rec->opts.auxtrace_snapshot_mode || rec->switch_output.enabled) {
 		signal(SIGUSR2, snapshot_sig_handler);
 		if (rec->opts.auxtrace_snapshot_mode)
 			trigger_on(&auxtrace_snapshot_trigger);
-		if (rec->switch_output.signal)
+		if (rec->switch_output.enabled)
 			trigger_on(&switch_output_trigger);
 	} else {
 		signal(SIGUSR2, SIG_IGN);
@@ -1361,6 +1380,14 @@ out_free:
 static int switch_output_setup(struct record *rec)
 {
 	struct switch_output *s = &rec->switch_output;
+	static struct parse_tag tags_size[] = {
+		{ .tag  = 'B', .mult = 1       },
+		{ .tag  = 'K', .mult = 1 << 10 },
+		{ .tag  = 'M', .mult = 1 << 20 },
+		{ .tag  = 'G', .mult = 1 << 30 },
+		{ .tag  = 0 },
+	};
+	unsigned long val;
 
 	if (!s->set)
 		return 0;
@@ -1368,10 +1395,22 @@ static int switch_output_setup(struct record *rec)
 	if (!strcmp(s->str, "signal")) {
 		s->signal = true;
 		pr_debug("switch-output with SIGUSR2 signal\n");
-		return 0;
+		goto enabled;
+	}
+
+	val = parse_tag_value(s->str, tags_size);
+	if (val != (unsigned long) -1) {
+		s->size = val;
+		pr_debug("switch-output with %s size threshold\n", s->str);
+		goto enabled;
 	}
 
 	return -1;
+
+enabled:
+	rec->timestamp_filename = true;
+	s->enabled              = true;
+	return 0;
 }
 
 static const char * const __record_usage[] = {
@@ -1542,8 +1581,9 @@ static struct option __record_options[] = {
 	OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
 		    "append timestamp to output filename"),
 	OPT_STRING_OPTARG_SET(0, "switch-output", &record.switch_output.str,
-			  &record.switch_output.set, "signal",
-			  "Switch output when receive SIGUSR2", "signal"),
+			  &record.switch_output.set, "signal,size",
+			  "Switch output when receive SIGUSR2 or cross size threshold",
+			  "signal"),
 	OPT_BOOLEAN(0, "dry-run", &dry_run,
 		    "Parse options then exit"),
 	OPT_END()
@@ -1606,9 +1646,6 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 		return -EINVAL;
 	}
 
-	if (rec->switch_output.signal)
-		rec->timestamp_filename = true;
-
 	if (!rec->itr) {
 		rec->itr = auxtrace_record__init(rec->evlist, &err);
 		if (err)
@@ -1657,7 +1694,7 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 
 	if (rec->no_buildid_cache || rec->no_buildid) {
 		disable_buildid_cache();
-	} else if (rec->switch_output.signal) {
+	} else if (rec->switch_output.enabled) {
 		/*
 		 * In 'perf record --switch-output', disable buildid
 		 * generation by default to reduce data file switching
@@ -1749,6 +1786,8 @@ out:
 
 static void snapshot_sig_handler(int sig __maybe_unused)
 {
+	struct record *rec = &record;
+
 	if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
 		trigger_hit(&auxtrace_snapshot_trigger);
 		auxtrace_record__snapshot_started = 1;
@@ -1756,6 +1795,6 @@ static void snapshot_sig_handler(int sig __maybe_unused)
 			trigger_error(&auxtrace_snapshot_trigger);
 	}
 
-	if (trigger_is_ready(&switch_output_trigger))
+	if (switch_output_signal(rec))
 		trigger_hit(&switch_output_trigger);
 }