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perf trace: Provide a better explanation when mmap fails

tip:perf/urgent tip-bot for Arnaldo Carvalho de Melo 1 participant 1 message Dec 12, 2014 perf events

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Commit-ID:  e09b18d4907992d3d615b215c1abf585721b2810
Gitweb:     http://git.kernel.org/tip/e09b18d4907992d3d615b215c1abf585721b2810
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Thu, 11 Dec 2014 18:04:10 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
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@ssdandy ~]$ 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@ssdandy ~]$ trace -m 128 -e nanosleep sleep 2
2001.280 (2000.403 ms): nanosleep(rqtp: 0x7fff89a8a7f0) = 0
[acme@ssdandy ~]$

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

Cc Adrian Hunter <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc David Ahern <[email protected]>
Cc Don Zickus <[email protected]>
Cc Frederic Weisbecker <[email protected]>
Cc Jiri Olsa <[email protected]>
Cc Mike Galbraith <[email protected]>
Cc Namhyung Kim <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Link http://lkml.kernel.org/n/[email protected] open here
Signed-off-by Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/builtin-trace.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)
tools/perf/builtin-trace.c +6 -6
index 83a4835..327541e 100644
@@ -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));