linux-kernel - [PATCH 05/22] perf test: Reduce the sample_freq for the 'object code reading' test

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Date:	Fri, 19 Feb 2016 19:41:19 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Steven Noonan <steven@...inklabs.net>,
	Wang Nan <wangnan0@...wei.com>
Subject: [PATCH 05/22] perf test: Reduce the sample_freq for the 'object code reading' test

From: Arnaldo Carvalho de Melo <acme@...hat.com>

Using 4 kHz is not necessary and sometimes is more than what was
auto-tuned:

  # dmesg | grep max_sample_rate | tail -2
  [ 2499.144373] perf interrupt took too long (2501 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
  [ 3592.413606] perf interrupt took too long (5069 > 5000), lowering kernel.perf_event_max_sample_rate to 25000

Simulating a auto-tune of 2000 we make the test fail, as reported
by Steven Noonan for one of his machines, so reduce it to 500 HZ,
it is enough to get a good number of samples for this test:

  # perf test -v 21 2>&1  | grep '^Reading object code for memory address' | tee /tmp/out | tail -5
  Reading object code for memory address: 0x479f40
  Reading object code for memory address: 0x7f29b7eea80d
  Reading object code for memory address: 0x7f29b7eea80d
  Reading object code for memory address: 0x7f29b7eea800
  Reading object code for memory address: 0xffffffff813b2f23
  [root@...et ~]# wc -l /tmp/out
  40 /tmp/out
  [root@...et ~]#

For systems that auto-tune below that, the previous patches will tell the
user what is happening so that he may either ignore the result of this test or
bump /proc/sys/kernel/perf_event_max_sample_rate.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Steven Noonan <steven@...inklabs.net>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-6kufyy1iprdfzrbtuqgxir70@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/tests/code-reading.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index f84339cb7f95..afc9ad0a0515 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -439,7 +439,7 @@ static int do_test_code_reading(bool try_kcore)
 		.mmap_pages	     = UINT_MAX,
 		.user_freq	     = UINT_MAX,
 		.user_interval	     = ULLONG_MAX,
-		.freq		     = 4000,
+		.freq		     = 500,
 		.target		     = {
 			.uses_mmap   = true,
 		},
-- 
2.5.0