perf tools: Add hint for 'Too many events are opened.' error message

Enhancing the 'Too many events are opened.' error message with hint to
use use 'ulimit -n <limit>' command.

Before:

  $ perf record -e 'sched:*,syscalls:*' ls
  Error:
  Too many events are opened.
  Try again after reducing the number of events.

Now:

  $ perf record -e 'sched:*,syscalls:*' ls
  Error:
  Too many events are opened.
  Probably the maximum number of open file descriptors has been reached.
  Hint: Try again after reducing the number of events.
  Hint: Try increasing the limit with 'ulimit -n <limit>'

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1432587114-14924-1-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index c886b9f7a48d01b31c0eb541961faa4c02df3179..a3e36fc634dc40005e77f7b228ec8ffb5ad001af 100644 (file)
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2149,7 +2149,9 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
        case EMFILE:
                return scnprintf(msg, size, "%s",
                         "Too many events are opened.\n"
-                        "Try again after reducing the number of events.");
+                        "Probably the maximum number of open file descriptors has been reached.\n"
+                        "Hint: Try again after reducing the number of events.\n"
+                        "Hint: Try increasing the limit with 'ulimit -n <limit>'");
        case ENODEV:
                if (target->cpu_list)
                        return scnprintf(msg, size, "%s",