[tip:perfcounters/urgent] perf stat: Micro-optimize the code: memcpy is only required if no event is selected and !null_run

[tip-bot for Jaswinder Singh Rajput]

Commit-ID:  c3043569dc8fbe9228b76174f15d1a7152c48a20
Gitweb:     http://git.kernel.org/tip/c3043569dc8fbe9228b76174f15d1a7152c48a20
Author:     Jaswinder Singh Rajput <jaswinder@xxxxxxxxxx>
AuthorDate: Sat, 27 Jun 2009 23:49:09 +0530
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 28 Jun 2009 15:22:47 +0200

perf stat: Micro-optimize the code: memcpy is only required if no event is selected and !null_run

Set attrs and nr_counters if no event is selected and !null_run.

Setting of attrs should depend on number of counters,
so we need to memcpy only for sizeof(default_attrs)

Also set nr_counters as ARRAY_SIZE(default_attrs) in place of
hardcoded value.

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
LKML-Reference: <1246126749.32198.16.camel@xxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 tools/perf/builtin-stat.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 3840a70..3e5ea4e 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -46,7 +46,7 @@
 #include <sys/prctl.h>
 #include <math.h>
 
-static struct perf_counter_attr default_attrs[MAX_COUNTERS] = {
+static struct perf_counter_attr default_attrs[] = {
 
   { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_TASK_CLOCK	},
   { .type = PERF_TYPE_SOFTWARE, .config = PERF_COUNT_SW_CONTEXT_SWITCHES},
@@ -477,16 +477,17 @@ int cmd_stat(int argc, const char **argv, const char *prefix)
 {
 	int status;
 
-	memcpy(attrs, default_attrs, sizeof(attrs));
-
 	argc = parse_options(argc, argv, options, stat_usage, 0);
 	if (!argc)
 		usage_with_options(stat_usage, options);
 	if (run_count <= 0 || run_count > MAX_RUN)
 		usage_with_options(stat_usage, options);
 
-	if (!null_run && !nr_counters)
-		nr_counters = 8;
+	/* Set attrs and nr_counters if no event is selected and !null_run */
+	if (!null_run && !nr_counters) {
+		memcpy(attrs, default_attrs, sizeof(default_attrs));
+		nr_counters = ARRAY_SIZE(default_attrs);
+	}
 
 	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 	assert(nr_cpus <= MAX_NR_CPUS);
--
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