linux-kernel - [tip:perf/core] perf evlist: Expose perf_event_mlock_kb_in

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Message-ID: <tip-xay69plylwibpb3l4isrpl1k@git.kernel.org>
Date:	Sat, 16 Apr 2016 02:20:58 -0700
From:	tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, adrian.hunter@...el.com, tglx@...utronix.de,
	mingo@...nel.org, namhyung@...nel.org, dsahern@...il.com,
	milian.wolff@...b.com, hpa@...or.com, wangnan0@...wei.com,
	linux-kernel@...r.kernel.org, jolsa@...nel.org
Subject: [tip:perf/core] perf evlist: Expose perf_event_mlock_kb_in_pages()
 helper

Commit-ID:  f5e7150cd9a7779a54b192d21afb9245384db8bc
Gitweb:     http://git.kernel.org/tip/f5e7150cd9a7779a54b192d21afb9245384db8bc
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Fri, 15 Apr 2016 17:46:31 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Fri, 15 Apr 2016 17:46:31 -0300

perf evlist: Expose perf_event_mlock_kb_in_pages() helper

When the user doesn't set --mmap-pages, perf_evlist__mmap() will do it
by reading the maximum possible for a non-root user from the
/proc/sys/kernel/perf_event_mlock_kb file.

Expose that function so that 'perf trace' can, for root users, to bump
mmap-pages to a higher value for root, based on the contents of this
proc file.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Milian Wolff <milian.wolff@...b.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-xay69plylwibpb3l4isrpl1k@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/evlist.c | 42 +++++++++++++++++++++++++-----------------
 tools/perf/util/evlist.h |  2 ++
 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 4c9f510..6fb5725 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -986,26 +986,34 @@ out_unmap:
 	return -1;
 }
 
-static size_t perf_evlist__mmap_size(unsigned long pages)
+unsigned long perf_event_mlock_kb_in_pages(void)
 {
-	if (pages == UINT_MAX) {
-		int max;
+	unsigned long pages;
+	int max;
 
-		if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
-			/*
-			 * Pick a once upon a time good value, i.e. things look
-			 * strange since we can't read a sysctl value, but lets not
-			 * die yet...
-			 */
-			max = 512;
-		} else {
-			max -= (page_size / 1024);
-		}
+	if (sysctl__read_int("kernel/perf_event_mlock_kb", &max) < 0) {
+		/*
+		 * Pick a once upon a time good value, i.e. things look
+		 * strange since we can't read a sysctl value, but lets not
+		 * die yet...
+		 */
+		max = 512;
+	} else {
+		max -= (page_size / 1024);
+	}
+
+	pages = (max * 1024) / page_size;
+	if (!is_power_of_2(pages))
+		pages = rounddown_pow_of_two(pages);
 
-		pages = (max * 1024) / page_size;
-		if (!is_power_of_2(pages))
-			pages = rounddown_pow_of_two(pages);
-	} else if (!is_power_of_2(pages))
+	return pages;
+}
+
+static size_t perf_evlist__mmap_size(unsigned long pages)
+{
+	if (pages == UINT_MAX)
+		pages = perf_event_mlock_kb_in_pages();
+	else if (!is_power_of_2(pages))
 		return 0;
 
 	return (pages + 1) * page_size;
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index da46423..208897a 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -158,6 +158,8 @@ int perf_evlist__parse_mmap_pages(const struct option *opt,
 				  const char *str,
 				  int unset);
 
+unsigned long perf_event_mlock_kb_in_pages(void);
+
 int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
 			 bool overwrite, unsigned int auxtrace_pages,
 			 bool auxtrace_overwrite);