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SubjectRe: [PATCH] perf tool: Round mmap pages to power 2
On 08/11/13 06:36, David Ahern wrote:
> 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)
> ...

This prevents:

--out-pages=0

from working e.g.

tools/perf/perf record -vv --out-pages=0 uname
rounding mmap pages size to 4096 (1 pages)

Although without this patch:

tools/perf/perf record -vv --out-pages=0 uname
--mmap_pages/-m value must be a power of two.
usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]

--out-pages <pages>
Number of pages or size with units to use for
output (default 64M)

Also there is:

tools/perf/perf record -vv --no-out-pages uname
Segmentation fault (core dumped)



> 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;



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