perf tools: Add unit_number__scnprintf function

Add unit_number__scnprintf function to display size units and use it in
-m option info message.

Before:
  $ perf record -m 10M ls
  rounding mmap pages size to 16777216 bytes (4096 pages)
  ...

After:
  $ perf record -m 10M ls
  rounding mmap pages size to 16M (4096 pages)
  ...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1483955520-29063-2-git-send-email-jolsa@kernel.org
[ Rename it to unit_number__scnprintf for consistency ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -1224,12 +1224,16 @@ static long parse_pages_arg(const char *str, unsigned long min,
 	if (pages == 0 && min == 0) {
 		/* leave number of pages at 0 */
 	} else if (!is_power_of_2(pages)) {
+		char buf[100];
+
 		/* round pages up to next power of 2 */
 		pages = roundup_pow_of_two(pages);
 		if (!pages)
 			return -EINVAL;
-		pr_info("rounding mmap pages size to %lu bytes (%lu pages)\n",
-			pages * page_size, pages);
+
+		unit_number__scnprintf(buf, sizeof(buf), pages * page_size);
+		pr_info("rounding mmap pages size to %s (%lu pages)\n",
+			buf, pages);
 	}
 
 	if (pages > max)