linux-kernel - [tip:perf/urgent] perf evlist: Fixup brown paper bag on "hint" for --mmap-pages cmdline arg

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Message-ID: <tip-8qope8lxb898narnq5kmu2gf@git.kernel.org>
Date:	Wed, 17 Dec 2014 22:28:06 -0800
From:	tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	mingo@...nel.org, paulus@...ba.org, dsahern@...il.com,
	namhyung@...nel.org, dzickus@...hat.com, acme@...hat.com,
	eranian@...gle.com, hpa@...or.com, efault@....de, jolsa@...hat.com,
	peterz@...radead.org, adrian.hunter@...el.com, bp@...e.de,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	fweisbec@...il.com
Subject: [tip:perf/urgent] perf evlist: Fixup brown paper bag on "hint"
  for --mmap-pages cmdline arg

Commit-ID:  0a2138b28fd56eeb3852133691c881409885ee3f
Gitweb:     http://git.kernel.org/tip/0a2138b28fd56eeb3852133691c881409885ee3f
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Fri, 12 Dec 2014 16:07:47 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 16 Dec 2014 13:38:26 -0300

perf evlist: Fixup brown paper bag on "hint" for --mmap-pages cmdline arg

When failing due to asking for a number of mmap pages that is more than
the max, it was suggesting that an even bigger number of mmap pages
should be specified, doh, au contraire!

Before:

  [acme@...andy linux]$ trace -m 128 usleep 1
  Error:	Operation not permitted.
  Hint:	Check /proc/sys/kernel/perf_event_mlock_kb (516 kB) setting.
  Hint:	Tried using 516 kB.
  Hint:	Try using a bigger -m/--mmap-pages value.
  [acme@...andy linux]$

After:

  [acme@...andy linux]$ trace -m 128 usleep 1
  Error:	Operation not permitted.
  Hint:	Check /proc/sys/kernel/perf_event_mlock_kb (516 kB) setting.
  Hint:	Tried using 516 kB.
  Hint:	Try using a smaller -m/--mmap-pages value.
  [acme@...andy linux]$

And to (really) clarify what happens above, when what the user requests
is <= max and even then it fails, a changeset is being made to tell that
this is a per user limit, not per process (in the above example there
was another 'perf trace' running for this user, which was using all the
pages it could use).

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: David Ahern <dsahern@...il.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/n/tip-8qope8lxb898narnq5kmu2gf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/evlist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index bb5dfc5..de7515d 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1495,7 +1495,7 @@ int perf_evlist__strerror_mmap(struct perf_evlist *evlist, int err, char *buf, s
 		scnprintf(buf, size, "Error:\t%s.\n"
 				     "Hint:\tCheck /proc/sys/kernel/perf_event_mlock_kb (%d kB) setting.\n"
 				     "Hint:\tTried using %zd kB.\n"
-				     "Hint:\tTry using a bigger -m/--mmap-pages value.",
+				     "Hint:\tTry using a smaller -m/--mmap-pages value.",
 				     emsg, value, evlist->mmap_len / 1024);
 		break;
 	default:
--
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