linux-kernel - [tip:perf/urgent] perf trace: Provide a better explanation when mmap fails

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Date:	Fri, 12 Dec 2014 00:20:11 -0800
From:	tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	fweisbec@...il.com, jolsa@...hat.com, adrian.hunter@...el.com,
	mingo@...nel.org, dsahern@...il.com, acme@...hat.com,
	hpa@...or.com, linux-kernel@...r.kernel.org, dzickus@...hat.com,
	peterz@...radead.org, bp@...e.de, efault@....de,
	namhyung@...nel.org, paulus@...ba.org, tglx@...utronix.de,
	eranian@...gle.com
Subject: [tip:perf/urgent] perf trace:
  Provide a better explanation when mmap fails

Commit-ID:  e09b18d4907992d3d615b215c1abf585721b2810
Gitweb:     http://git.kernel.org/tip/e09b18d4907992d3d615b215c1abf585721b2810
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Thu, 11 Dec 2014 18:04:10 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 11 Dec 2014 18:04:10 -0300

perf trace: Provide a better explanation when mmap fails

If we ask for a mmap lenght than the max configured via the relevant
sysctl, provide a better warning, instead of just expanding the EPERM
returned:

[acme@...andy ~]$ trace -m 256 -e nanosleep sleep 2
Error:	Operation not permitted.
Hint:	Check /proc/sys/kernel/perf_event_mlock_kb (516 kB) setting.
Hint:	Tried using 1028 kB.
Hint:	Try using a bigger -m/--mmap-pages value.

[acme@...andy ~]$ trace -m 128 -e nanosleep sleep 2
  2001.280 (2000.403 ms): nanosleep(rqtp: 0x7fff89a8a7f0) = 0
[acme@...andy ~]$

An upcoming patch will autotune the request for non-root users when -m
is not used.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: David Ahern <dsahern@...il.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lkml.kernel.org/n/tip-cdvxfz2gycetbkopm9sna1qp@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/builtin-trace.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 83a4835..327541e 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2045,7 +2045,6 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 	unsigned long before;
 	const bool forks = argc > 0;
 	bool draining = false;
-	char sbuf[STRERR_BUFSIZE];
 
 	trace->live = true;
 
@@ -2106,11 +2105,8 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
 		goto out_error_open;
 
 	err = perf_evlist__mmap(evlist, trace->opts.mmap_pages, false);
-	if (err < 0) {
-		fprintf(trace->output, "Couldn't mmap the events: %s\n",
-			strerror_r(errno, sbuf, sizeof(sbuf)));
-		goto out_delete_evlist;
-	}
+	if (err < 0)
+		goto out_error_mmap;
 
 	perf_evlist__enable(evlist);
 
@@ -2210,6 +2206,10 @@ out_error_tp:
 	perf_evlist__strerror_tp(evlist, errno, errbuf, sizeof(errbuf));
 	goto out_error;
 
+out_error_mmap:
+	perf_evlist__strerror_mmap(evlist, errno, errbuf, sizeof(errbuf));
+	goto out_error;
+
 out_error_open:
 	perf_evlist__strerror_open(evlist, errno, errbuf, sizeof(errbuf));
 
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