linux-kernel - [PATCH 1/2] perf lock contention: Fix debug stat if no contention

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Date:   Mon, 27 Mar 2023 15:57:10 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org, Hao Luo <haoluo@...gle.com>,
        bpf@...r.kernel.org
Subject: [PATCH 1/2] perf lock contention: Fix debug stat if no contention

It should not divide if the total number is 0.  Otherwise it'd show
NaN in the bad rate output.  Also add a whitespace in the "output
for debug" message.

  $ sudo perf lock contention -abv true
  Looking at the vmlinux_path (8 entries long)
  symsrc__init: cannot get elf header.
  Using /proc/kcore for kernel data
  Using /proc/kallsyms for symbols
   contended   total wait     max wait     avg wait         type   caller

  === output for debug===

  bad: 0, total: 0
  bad rate: -nan %     <-------------------------  (here)
  histogram of events caused bad sequence
      acquire: 0
     acquired: 0
    contended: 0
      release: 0

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-lock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 3c8a19ebc496..82dd2dfe5692 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -1323,10 +1323,10 @@ static void print_bad_events(int bad, int total)
 	for (i = 0; i < BROKEN_MAX; i++)
 		broken += bad_hist[i];
 
-	if (quiet || (broken == 0 && verbose <= 0))
+	if (quiet || total == 0 || (broken == 0 && verbose <= 0))
 		return;
 
-	pr_info("\n=== output for debug===\n\n");
+	pr_info("\n=== output for debug ===\n\n");
 	pr_info("bad: %d, total: %d\n", bad, total);
 	pr_info("bad rate: %.2f %%\n", (double)bad / (double)total * 100);
 	pr_info("histogram of events caused bad sequence\n");
-- 
2.40.0.348.gf938b09366-goog