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 <mingo@kernel.org>
Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1384267617-3446-3-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 6 insertions, 12 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 3960560f873a..fb4727d3df85 100644
--- a/tools/perf/util/evlist.c
+++ b/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;
         }