perf top: Add error message for EMFILE

When a user tries to open so many events, perf_event_open syscall may
fail with EMFILE. Provide advise for that case.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1325957132-10600-3-git-send-email-namhyung@gmail.com
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index d89dec90103..8f80df89603 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -888,6 +888,10 @@ try_again:
                                 ui__warning("The %s event is not supported.\n",
                                             event_name(counter));
                                 goto out_err;
+                        } else if (err == EMFILE) {
+                                ui__warning("Too many events are opened.\n"
+                                            "Try again after reducing the number of events\n");
+                                goto out_err;
                         }
 
                         ui__warning("The sys_perf_event_open() syscall "