[PATCH 4/4] perf record: add option to set the number of thread for event synthesize

[kan . liang]

From: Kan Liang <Kan.liang@xxxxxxxxx>

Using UINT_MAX to indicate the default thread#, which is the number of
online CPU.

Signed-off-by: Kan Liang <Kan.liang@xxxxxxxxx>
---
 tools/perf/Documentation/perf-record.txt |  4 ++++
 tools/perf/builtin-record.c              | 13 +++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 68a1ffb..f759dc4 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -483,6 +483,10 @@ config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'.
 
 Implies --tail-synthesize.
 
+--num-thread-synthesize::
+The number of threads to run event synthesize.
+By default, the number of threads equals to the online CPU number.
+
 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 1978021..98bb547 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -86,6 +86,7 @@ struct record {
 	struct switch_output	switch_output;
 	unsigned long long	samples;
 	struct synthesize_buf	*buf;
+	unsigned int		nr_threads_synthesize;
 };
 
 static volatile int auxtrace_record__snapshot_started;
@@ -722,7 +723,12 @@ static int record__multithread_synthesize(struct record *rec,
 					  struct perf_tool *tool,
 					  struct record_opts *opts)
 {
-	int i, err, nr_thread = sysconf(_SC_NPROCESSORS_ONLN);
+	int i, err, nr_thread;
+
+	if (rec->nr_threads_synthesize == UINT_MAX)
+		nr_thread = sysconf(_SC_NPROCESSORS_ONLN);
+	else
+		nr_thread = rec->nr_threads_synthesize;
 
 	if (nr_thread > 1) {
 		perf_set_multithreaded();
@@ -836,7 +842,7 @@ static int record__synthesize(struct record *rec, bool tail)
 	}
 
 	/* multithreading synthesize is only available for cpu monitoring */
-	if (target__has_cpu(&opts->target))
+	if (target__has_cpu(&opts->target) && (rec->nr_threads_synthesize > 1))
 		err = record__multithread_synthesize(rec, machine, tool, opts);
 	else
 		err = __machine__synthesize_threads(machine, tool,
@@ -1521,6 +1527,7 @@ static struct record record = {
 		.mmap2		= perf_event__process_mmap2,
 		.ordered_events	= true,
 	},
+	.nr_threads_synthesize = UINT_MAX,
 };
 
 const char record_callchain_help[] = CALLCHAIN_RECORD_HELP
@@ -1662,6 +1669,8 @@ static struct option __record_options[] = {
 			  "signal"),
 	OPT_BOOLEAN(0, "dry-run", &dry_run,
 		    "Parse options then exit"),
+	OPT_UINTEGER(0, "num-thread-synthesize", &record.nr_threads_synthesize,
+			"number of thread to run event synthesize"),
 	OPT_END()
 };
 
-- 
2.7.4