[PATCH RFC V4 4/6] perf top: 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 max number
of online CPU.

Signed-off-by: Kan Liang <kan.li...@intel.com>
---
 tools/perf/Documentation/perf-top.txt |  3 +++
 tools/perf/builtin-top.c              | 11 ++++++++---
 tools/perf/util/event.c               |  5 ++++-
 tools/perf/util/top.h                 |  1 +
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/perf/Documentation/perf-top.txt 
b/tools/perf/Documentation/perf-top.txt
index d864ea6..c3cc9a3 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -240,6 +240,9 @@ Default is to monitor all CPUS.
 --force::
        Don't do ownership validation.
 
+--num-thread-synthesize::
+       The number of threads to run event synthesize.
+       By default, the number of threads equals to the online CPU number.
 
 INTERACTIVE PROMPTING KEYS
 --------------------------
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index bc31b93..477a869 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -958,14 +958,16 @@ static int __cmd_top(struct perf_top *top)
        if (perf_session__register_idle_thread(top->session) < 0)
                goto out_delete;
 
-       perf_set_multithreaded();
+       if (top->nr_threads_synthesize > 1)
+               perf_set_multithreaded();
 
        machine__synthesize_threads(&top->session->machines.host, &opts->target,
                                    top->evlist->threads, false,
                                    opts->proc_map_timeout,
-                                   (unsigned 
int)sysconf(_SC_NPROCESSORS_ONLN));
+                                   top->nr_threads_synthesize);
 
-       perf_set_singlethreaded();
+       if (top->nr_threads_synthesize > 1)
+               perf_set_singlethreaded();
 
        if (perf_hpp_list.socket) {
                ret = perf_env__read_cpu_topology_map(&perf_env);
@@ -1118,6 +1120,7 @@ int cmd_top(int argc, const char **argv)
                },
                .max_stack           = sysctl_perf_event_max_stack,
                .sym_pcnt_filter     = 5,
+               .nr_threads_synthesize = UINT_MAX,
        };
        struct record_opts *opts = &top.record_opts;
        struct target *target = &opts->target;
@@ -1227,6 +1230,8 @@ int cmd_top(int argc, const char **argv)
        OPT_BOOLEAN(0, "hierarchy", &symbol_conf.report_hierarchy,
                    "Show entries in a hierarchy"),
        OPT_BOOLEAN(0, "force", &symbol_conf.force, "don't complain, do it"),
+       OPT_UINTEGER(0, "num-thread-synthesize", &top.nr_threads_synthesize,
+                       "number of thread to run event synthesize"),
        OPT_END()
        };
        const char * const top_usage[] = {
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 0e678dd..47eff47 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -790,7 +790,10 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
        if (n < 0)
                return err;
 
-       thread_nr = nr_threads_synthesize;
+       if (nr_threads_synthesize == UINT_MAX)
+               thread_nr = sysconf(_SC_NPROCESSORS_ONLN);
+       else
+               thread_nr = nr_threads_synthesize;
 
        if (thread_nr <= 1) {
                err = __perf_event__synthesize_threads(tool, process,
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index 9bdfb78..f4296e1 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -37,6 +37,7 @@ struct perf_top {
        int                sym_pcnt_filter;
        const char         *sym_filter;
        float              min_percent;
+       unsigned int       nr_threads_synthesize;
 };
 
 #define CONSOLE_CLEAR ""
-- 
2.5.5