[tip:perf/core] perf evsel: Inform how to make a sysctl setting permanent

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  d6195a6a2c247515d5832debb51c03a74dc3f8f6
Gitweb:     http://git.kernel.org/tip/d6195a6a2c247515d5832debb51c03a74dc3f8f6
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Mon, 13 Feb 2017 16:45:24 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 13 Feb 2017 17:22:33 -0300

perf evsel: Inform how to make a sysctl setting permanent

When a tool can't open counters due to the kernel.perf_event_paranoit
sysctl setting, we inform how to tweak it to allow the operation to
succeed, in addition to that, suggest setting /etc/sysctl.conf to
make the setting permanent.

Suggested-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-4gwe99k4a6p12d4u8bbyttj2@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-record.c | 2 +-
 tools/perf/builtin-stat.c   | 2 +-
 tools/perf/builtin-top.c    | 2 +-
 tools/perf/util/evsel.c     | 4 +++-
 4 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ffac8ca..2ddf189 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -418,7 +418,7 @@ static int record__mmap(struct record *rec)
 
 static int record__open(struct record *rec)
 {
-	char msg[512];
+	char msg[BUFSIZ];
 	struct perf_evsel *pos;
 	struct perf_evlist *evlist = rec->evlist;
 	struct perf_session *session = rec->session;
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index a02f2e9..f287191 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -533,7 +533,7 @@ static int store_counter_ids(struct perf_evsel *counter)
 static int __run_perf_stat(int argc, const char **argv)
 {
 	int interval = stat_config.interval;
-	char msg[512];
+	char msg[BUFSIZ];
 	unsigned long long t0, t1;
 	struct perf_evsel *counter;
 	struct timespec ts;
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index d90927f..5a7fd7a 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -859,7 +859,7 @@ static void perf_top__mmap_read(struct perf_top *top)
 
 static int perf_top__start_counters(struct perf_top *top)
 {
-	char msg[512];
+	char msg[BUFSIZ];
 	struct perf_evsel *counter;
 	struct perf_evlist *evlist = top->evlist;
 	struct record_opts *opts = &top->record_opts;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 04e536a..cd2fb42 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2469,7 +2469,9 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 		 "  -1: Allow use of (almost) all events by all users\n"
 		 ">= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK\n"
 		 ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"
-		 ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN",
+		 ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN\n\n"
+		 "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
+		 "	kernel.perf_event_paranoid = -1\n" ,
 				 target->system_wide ? "system-wide " : "",
 				 perf_event_paranoid());
 	case ENOENT: