linux-kernel - [PATCH v2 2/2] perf: Add error message for EMFILE

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Date:	Tue, 31 Jan 2012 10:15:16 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: [PATCH v2 2/2] perf: Add error message for EMFILE

When a user tries to open so many event on multiple tasks/cpus,
perf_event_open syscall may fail with EMFILE. Provide an advice
for that case.

Signed-off-by: Namhyung Kim <namhyung.kim@....com>
Cc: David Ahern <dsahern@...il.com>
---
 tools/perf/builtin-record.c |    5 +++++
 tools/perf/builtin-stat.c   |    4 ++++
 tools/perf/builtin-top.c    |    3 ++-
 3 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 32870eef952f..a334008a1853 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -249,6 +249,11 @@ try_again:
 				ui__warning("The %s event is not supported.\n",
 					    event_name(pos));
 				exit(EXIT_FAILURE);
+			} else if (err == EMFILE) {
+				ui__warning("Too many events are opened.\n"
+					    "Try again after reducing the number of events,\n"
+					    "tasks and/or cpus.\n");
+				exit(EXIT_FAILURE);
 			}
 
 			printf("\n");
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 459b8620a5d9..7c5421c7af06 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -477,6 +477,10 @@ static int run_perf_stat(int argc __used, const char **argv)
 				      "\t Consider tweaking"
 				      " /proc/sys/kernel/perf_event_paranoid or running as root.",
 				      system_wide ? "system-wide " : "");
+			} else if (errno == EMFILE) {
+				error("Too many events are opened.\n"
+				      "\t Try again after reducing the number of events,\n"
+				      "\t tasks and/or cpus.");
 			} else {
 				error("open_counter returned with %d (%s). "
 				      "/bin/dmesg may provide additional information.\n",
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index e8b033c074f9..987af3695218 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -899,7 +899,8 @@ try_again:
 				goto out_err;
 			} else if (err == EMFILE) {
 				ui__warning("Too many events are opened.\n"
-					    "Try again after reducing the number of events\n");
+					    "Try again after reducing the number of events,\n"
+					    "tasks and/or cpus.\n");
 				goto out_err;
 			}
 
-- 
1.7.9.rc1.dirty

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