perf evlist: Round mmap pages to power 2 - v2

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)
  ...

v2: Add bytes units to rounding message per Ingo's request. Other
    suggestions (e.g., prefixing INFO) should be addressed by wrapping
    pr_info to catch all instances.

Suggested-by: Ingo Molnar <[email protected]>
Signed-off-by: David Ahern <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/evlist.c

@@ -710,7 +710,6 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
 {
 	unsigned int *mmap_pages = opt->value;
 	unsigned long pages, val;
-	size_t size;
 	static struct parse_tag tags[] = {
 		{ .tag  = 'B', .mult = 1       },
 		{ .tag  = 'K', .mult = 1 << 10 },
@@ -726,11 +725,6 @@ 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;
@@ -741,14 +735,14 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
 		}
 	}
 
-	if (pages > UINT_MAX || pages > SIZE_MAX / page_size) {
-		pr_err("--mmap_pages/-m value too big\n");
-		return -1;
+	if (pages < (1UL << 31) && !is_power_of_2(pages)) {
+		pages = next_pow2(pages);
+		pr_info("rounding mmap pages size to %lu bytes (%lu pages)\n",
+			pages * page_size, pages);
 	}
 
-	size = perf_evlist__mmap_size(pages);
-	if (!size) {
-		pr_err("--mmap_pages/-m value must be a power of two.");
+	if (pages > UINT_MAX || pages > SIZE_MAX / page_size) {
+		pr_err("--mmap_pages/-m value too big\n");
 		return -1;
 	}