[PATCH] perf, tools: Fix adding multiple event groups

[Andi Kleen <andi@firstfloor.org>]

From: Andi Kleen <ak@linux.intel.com>

The -M metric group parser threw away the events of earlier
groups when multiple groups were specified. Fix this here
by not overwriting the string incorrectly.

Now this works correctly:

% perf stat -M Summary,SMT --metric-only -a sleep 1

 Performance counter stats for 'system wide':

Instructions         CPI                  CLKS                 CPU_Utilization      GFLOPs               SMT_2T_Utilization   SMT_2T_Utilization   Kernel_Utilization   CoreIPC              CORE_CLKS
900907376.0              2.7            2398954144.0             0.1                 0.0                 0.2                 0.2                 0.1                 0.4            2080822855.5

while previously it would only show the SMT metrics.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/util/metricgroup.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 0794f02cbb8f..ce18474adc12 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -373,9 +373,6 @@ static int metricgroup__add_metric(const char *metric, struct strbuf *events,
 	int ret = -EINVAL;
 	int i, j;
 
-	strbuf_init(events, 100);
-	strbuf_addf(events, "%s", "");
-
 	if (!map)
 		return 0;
 
@@ -433,6 +430,10 @@ static int metricgroup__add_metric_list(const char *list, struct strbuf *events,
 	if (!nlist)
 		return -ENOMEM;
 	llist = nlist;
+
+	strbuf_init(events, 100);
+	strbuf_addf(events, "%s", "");
+
 	while ((p = strsep(&llist, ",")) != NULL) {
 		ret = metricgroup__add_metric(p, events, group_list);
 		if (ret == -EINVAL) {
-- 
2.9.5