Re: [PATCH 10/28] perf report: Cache cumulative callchains

Jiri Olsa
2014-01-11T16:03:21Z

On Wed, Jan 08, 2014 at 05:46:15PM +0900, Namhyung Kim wrote:
> It is possble that a callchain has cycles or recursive calls. In that
> case it'll end up having entries more than 100% overhead in the
> output. In order to prevent such entries, cache each callchain node
> and skip if same entry already cumulated.
>
> Cc: Arun Sharma <asharma@fb.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
> tools/perf/builtin-report.c | 54 ++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index 06330736485b..087d01cac1aa 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -363,7 +363,27 @@ static int
> iter_prepare_cumulative_entry(struct hist_entry_iter *iter __maybe_unused,
> struct addr_location *al __maybe_unused)
> {
> + struct callchain_cursor_node *node;
> + struct hist_entry **he_cache;
> +
> callchain_cursor_commit(&callchain_cursor);
> +
> + /*
> + * This is for detecting cycles or recursions so that they're
> + * cumulated only one time to prevent entries more than 100%
> + * overhead.
> + */
> + he_cache = malloc(sizeof(*he_cache) * (PERF_MAX_STACK_DEPTH + 1));
> + if (he_cache == NULL)
> + return -ENOMEM;
> +
> + iter->priv = he_cache;
> + iter->curr = 0;
> +
> + node = callchain_cursor_current(&callchain_cursor);
> + if (node == NULL)
> + return 0;

some leftover? looks like nop..

jirka

> +
> return 0;
> }
>

SNIP