perf evlist: Add suggestion of how to set perf_event_paranoid sysctl

Minor hint to speed up problem resolution and get 'trace' working for
non root users.

Cc: Adrian Hunter <adrian.hunter@intel.com>
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-abdqi8km4fj9osrn70q2zj9v@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 59ef2802fcf631fa0e7d6f2f97e59e6881f675d4..c51223ac25f4854ea12802eb4f163c6b5cdfa0b4 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1214,10 +1214,11 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
                                             "For your workloads it needs to be <= 1\nHint:\t");
                }
                printed += scnprintf(buf + printed, size - printed,
-                                    "For system wide tracing it needs to be set to -1");
+                                    "For system wide tracing it needs to be set to -1.\n");
 
                printed += scnprintf(buf + printed, size - printed,
-                                   ".\nHint:\tThe current value is %d.", value);
+                                   "Hint:\tTry: 'sudo sh -c \"echo -1 > /proc/sys/kernel/perf_event_paranoid\"'\n"
+                                   "Hint:\tThe current value is %d.", value);
                break;
        default:
                scnprintf(buf, size, "%s", emsg);