linux-kernel - [tip:perf/core] perf stat: Don't print bogus data on -e cycles

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Date:	Mon, 14 Oct 2013 22:29:16 -0700
From:	tip-bot for Ramkumar Ramachandra <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, paulus@...ba.org,
	hpa@...or.com, mingo@...nel.org, a.p.zijlstra@...llo.nl,
	tglx@...utronix.de, artagnon@...il.com
Subject: [tip:perf/core] perf stat: Don't print bogus data on -e cycles

Commit-ID:  c458fe62ca31496664c1211a7906d261220b18f9
Gitweb:     http://git.kernel.org/tip/c458fe62ca31496664c1211a7906d261220b18f9
Author:     Ramkumar Ramachandra <artagnon@...il.com>
AuthorDate: Mon, 30 Sep 2013 16:43:05 +0530
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Fri, 11 Oct 2013 12:17:33 -0300

perf stat: Don't print bogus data on -e cycles

When only the cycles event is requested:

$ perf stat -e cycles dd if=/dev/zero of=/dev/null count=1000000
1000000+0 records in
1000000+0 records out
512000000 bytes (512 MB) copied, 0.26123 s, 2.0 GB/s

 Performance counter stats for 'dd if=/dev/zero of=/dev/null count=1000000':

       911,626,453 cycles                    #    0.000 GHz

       0.262113350 seconds time elapsed

The 0.000 GHz comment in the output is totally bogus and misleading. It
happens because update_shadow_stats() doesn't touch runtime_nsecs_stats;
it is only written when a requested counter matches a SW_TASK_CLOCK. In
our case, since we have only requested HW_CPU_CYCLES,
runtime_nsecs_stats is unavailable. So, omit printing the comment
altogether.

Signed-off-by: Ramkumar Ramachandra <artagnon@...il.com>
Acked-by: Ingo Molnar <mingo@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1380539585-23859-3-git-send-email-artagnon@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-stat.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 700b478..ce2266c 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -997,10 +997,10 @@ static void abs_printout(int cpu, int nr, struct perf_evsel *evsel, double avg)
 	} else if (perf_evsel__match(evsel, HARDWARE, HW_CPU_CYCLES)) {
 		total = avg_stats(&runtime_nsecs_stats[cpu]);
 
-		if (total)
-			ratio = 1.0 * avg / total;
-
-		fprintf(output, " # %8.3f GHz                    ", ratio);
+		if (total) {
+			ratio = avg / total;
+			fprintf(output, " # %8.3f GHz                    ", ratio);
+		}
 	} else if (transaction_run &&
 		   perf_evsel__cmp(evsel, nth_evsel(T_CYCLES_IN_TX))) {
 		total = avg_stats(&runtime_cycles_stats[cpu]);
--
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