linux-kernel - [PATCH] perf stat: Fix shadow stats for clock events

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Date:   Fri, 16 Nov 2018 09:58:43 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     acme@...nel.org, jolsa@...hat.com
Cc:     alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        yao.jin@...ux.intel.com, linux-kernel@...r.kernel.org,
        yuzhoujian@...ichuxing.com, tmricht@...ux.vnet.ibm.com,
        anton@...ba.org, Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: [PATCH] perf stat: Fix shadow stats for clock events

Commit 0aa802a79469 ("perf stat: Get rid of extra clock display
function") introduced scale and unit for clock events. Thus,
perf_stat__update_shadow_stats() now saves scaled values of
clock events in msecs, instead of original nsecs. But while
calculating values of shadow stats we still consider clock
event values in nsecs. This results in a wrong shadow stat
values. Ex,

  # ./perf stat -e task-clock,cycles ls
    <SNIP>
              2.60 msec task-clock:u    #    0.877 CPUs utilized
         2,430,564      cycles:u        # 1215282.000 GHz

Fix this by saving original nsec values for clock events in
perf_stat__update_shadow_stats(). After patch:

  # ./perf stat -e task-clock,cycles ls
    <SNIP>
              3.14 msec task-clock:u    #    0.839 CPUs utilized
         3,094,528      cycles:u        #    0.985 GHz

Reported-by: Anton Blanchard <anton@...ba.org>
Suggested-by: Jiri Olsa <jolsa@...hat.com>
Fixes: 0aa802a79469 ("perf stat: Get rid of extra clock display function")
Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
 tools/perf/util/stat-shadow.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index f0a8cec55c47..3c22c58b3e90 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -209,11 +209,12 @@ void perf_stat__update_shadow_stats(struct perf_evsel *counter, u64 count,
 				    int cpu, struct runtime_stat *st)
 {
 	int ctx = evsel_context(counter);
+	u64 count_ns = count;
 
 	count *= counter->scale;
 
 	if (perf_evsel__is_clock(counter))
-		update_runtime_stat(st, STAT_NSECS, 0, cpu, count);
+		update_runtime_stat(st, STAT_NSECS, 0, cpu, count_ns);
 	else if (perf_evsel__match(counter, HARDWARE, HW_CPU_CYCLES))
 		update_runtime_stat(st, STAT_CYCLES, ctx, cpu, count);
 	else if (perf_stat_evsel__is(counter, CYCLES_IN_TX))
-- 
2.17.1