perf: builtin-record: Document and check that mmap_pages must be a power of two.
Now that we automatically point users at it, let's provide them some
guidance so that they hopefully don't just get mysterious EINVAL's
from the kernel.
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1324301972-22740-4-git-send-email-nelhage@nelhage.com
Signed-off-by: Nelson Elhage <nelhage@nelhage.com>
[ committer note: Made it work after 50a682c ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 56bb447..e873ae2 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -279,6 +279,9 @@
"/proc/sys/kernel/perf_event_mlock_kb,\n"
"or try again with a smaller value of -m/--mmap_pages.\n"
"(current value: %d)\n", opts->mmap_pages);
+ else if (!is_power_of_2(opts->mmap_pages))
+ die("--mmap_pages/-m value must be a power of two.");
+
die("failed to mmap with %d (%s)\n", errno, strerror(errno));
}