Commit e965bea1 authored Dec 12, 2014 by Arnaldo Carvalho de Melo

perf evlist: Improve the strerror_mmap method

Considering the per user locked pages limit, improve the message when a
user uses multiple simultaneous perf mmap calls:

When the request is more than the current maximum:

  [acme@ssdandy linux]$ trace -m 128 usleep 1
  Error: Operation not permitted.
  Hint:  Check /proc/sys/kernel/perf_event_mlock_kb (516 kB) setting.
  Hint:  Tried using 516 kB.
  Hint:  Try 'sudo sh -c "echo 1032 > /proc/sys/kernel/perf_event_mlock_kb"', or
  Hint:  Try using a smaller -m/--mmap-pages value.
  [acme@ssdandy linux]$

And when the limit is less than that:

  [acme@ssdandy linux]$ trace -m 512 usleep 1
  Error: Operation not permitted.
  Hint:  Check /proc/sys/kernel/perf_event_mlock_kb (2056 kB) setting.
  Hint:  Tried using 2052 kB.
  Hint:  Try using a smaller -m/--mmap-pages value.
  [acme@ssdandy linux]$

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-yqdie3c8qvdgenwleri267d4@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent e5d4a290

tools/perf/util/evlist.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -1487,16 +1487,25 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
		int perf_evlist__strerror_mmap(struct perf_evlist evlist, int err, char buf, size_t size)
		{
		char sbuf[STRERR_BUFSIZE], *emsg = strerror_r(err, sbuf, sizeof(sbuf));
		int pages_attempted = evlist->mmap_len / 1024, pages_max_per_user;
		int pages_attempted = evlist->mmap_len / 1024, pages_max_per_user, printed = 0;

		switch (err) {
		case EPERM:
		sysctl__read_int("kernel/perf_event_mlock_kb", &pages_max_per_user);
		scnprintf(buf, size, "Error:\t%s.\n"
		printed += scnprintf(buf + printed, size - printed,
		"Error:\t%s.\n"
		"Hint:\tCheck /proc/sys/kernel/perf_event_mlock_kb (%d kB) setting.\n"
		"Hint:\tTried using %zd kB.\n"
		"Hint:\tTry using a smaller -m/--mmap-pages value.",
		"Hint:\tTried using %zd kB.\n",
		emsg, pages_max_per_user, pages_attempted);

		if (pages_attempted >= pages_max_per_user) {
		printed += scnprintf(buf + printed, size - printed,
		"Hint:\tTry 'sudo sh -c \"echo %d > /proc/sys/kernel/perf_event_mlock_kb\"', or\n",
		pages_max_per_user + pages_attempted);
		}

		printed += scnprintf(buf + printed, size - printed,
		"Hint:\tTry using a smaller -m/--mmap-pages value.");
		break;
		default:
		scnprintf(buf, size, "%s", emsg);