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

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Message-ID: <20140111160254.GD1131@krava.brq.redhat.com>
Date:	Sat, 11 Jan 2014 17:02:54 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arun Sharma <asharma@...com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Rodrigo Campos <rodrigo@...g.com.ar>
Subject: Re: [PATCH 10/28] perf report: Cache cumulative callchains

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@...com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.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
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