linux-kernel - [PATCH v0 11/71] perf tools: Add perf_event

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Date:	Wed, 11 Dec 2013 14:36:23 +0200
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH v0 11/71] perf tools: Add perf_event_paranoid()

From: Adrian Hunter <adrian.hunter@...el.com>

Add a function to return the value of
/proc/sys/kernel/perf_event_paranoid.

This will be used to determine default
values for mmap size because perf is not
subject to mmap limits when
perf_event_paranoid is less than zero.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/util/evlist.c |  3 +--
 tools/perf/util/util.c   | 19 +++++++++++++++++++
 tools/perf/util/util.h   |  3 +++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7bb6ee1..50fadde 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1189,8 +1189,7 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
 				    "Error:\t%s.\n"
 				    "Hint:\tCheck /proc/sys/kernel/perf_event_paranoid setting.", emsg);
 
-		if (filename__read_int("/proc/sys/kernel/perf_event_paranoid", &value))
-			break;
+		value = perf_event_paranoid();
 
 		printed += scnprintf(buf + printed, size - printed, "\nHint:\t");
 
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index bae8756..3aed4af 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -1,5 +1,6 @@
 #include "../perf.h"
 #include "util.h"
+#include "fs.h"
 #include <sys/mman.h>
 #ifdef HAVE_BACKTRACE_SUPPORT
 #include <execinfo.h>
@@ -8,6 +9,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#include <limits.h>
 #include <linux/kernel.h>
 
 /*
@@ -482,3 +484,20 @@ int filename__read_str(const char *filename, char **buf, size_t *sizep)
 	close(fd);
 	return err;
 }
+
+int perf_event_paranoid(void)
+{
+	char path[PATH_MAX];
+	const char *procfs = procfs__mountpoint();
+	int value;
+
+	if (!procfs)
+		return INT_MAX;
+
+	scnprintf(path, PATH_MAX, "%s/sys/kernel/perf_event_paranoid", procfs);
+
+	if (filename__read_int(path, &value))
+		return INT_MAX;
+
+	return value;
+}
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index adb39f2..4b6b260 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -309,4 +309,7 @@ void free_srcline(char *srcline);
 
 int filename__read_int(const char *filename, int *value);
 int filename__read_str(const char *filename, char **buf, size_t *sizep);
+
+int perf_event_paranoid(void);
+
 #endif /* GIT_COMPAT_UTIL_H */
-- 
1.8.5.1

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