[PATCH] perf tool: Round mmap pages to power 2

[David Ahern <dsahern@gmail.com>]

Currently perf requires the -m / --mmap_pages option to be a power of 2.
To be more user friendly perf should automatically round this up to the
next power of 2.

Currently:
  $ perf record -m 3 -a -- sleep 1
  --mmap_pages/-m value must be a power of two.sleep: Terminated

With patch:
  $ perf record -m 3 -a -- sleep 1
  rounding mmap pages size to 16384 (4 pages)
  ...

Signed-off-by: David Ahern <dsahern@gmail.com>
Suggested-by: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
---
 tools/perf/util/evlist.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index b939221efd8d..9ec3a5a45f22 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -722,11 +722,6 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
 	if (val != (unsigned long) -1) {
 		/* we got file size value */
 		pages = PERF_ALIGN(val, page_size) / page_size;
-		if (pages < (1UL << 31) && !is_power_of_2(pages)) {
-			pages = next_pow2(pages);
-			pr_info("rounding mmap pages size to %lu (%lu pages)\n",
-				pages * page_size, pages);
-		}
 	} else {
 		/* we got pages count value */
 		char *eptr;
@@ -737,6 +732,12 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
 		}
 	}
 
+	if (pages < (1UL << 31) && !is_power_of_2(pages)) {
+		pages = next_pow2(pages);
+		pr_info("rounding mmap pages size to %lu (%lu pages)\n",
+			pages * page_size, pages);
+	}
+
 	if (pages > UINT_MAX || pages > SIZE_MAX / page_size) {
 		pr_err("--mmap_pages/-m value too big\n");
 		return -1;
-- 
1.8.3.4 (Apple Git-47)