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

[kan . liang]

From: Kan Liang <kan.li...@intel.com>

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

Signed-off-by: Kan Liang <kan.li...@intel.com>
---
 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