From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Fri, 12 Dec 2014 19:07:47 +0000 (-0300)
Subject: perf evlist: Fixup brown paper bag on "hint" for --mmap-pages cmdline arg
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=0a2138b28fd56eeb3852133691c881409885ee3f;p=deliverable%2Flinux.git

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@ssdandy 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@ssdandy linux]$

After:

  [acme@ssdandy 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@ssdandy 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@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-8qope8lxb898narnq5kmu2gf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index bb5dfc5d1e75..de7515dd683a 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: