linux-kernel - Re: [PATCH V2 1/1] perf hists: clear dummy entry accumulated period

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Date:	Mon, 25 Apr 2016 10:24:17 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	kan.liang@...el.com
Cc:	acme@...nel.org, namhyung@...nel.org, jolsa@...nel.org,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/1] perf hists: clear dummy entry accumulated period

On Fri, Apr 22, 2016 at 12:58:58AM -0700, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
> 
> The accumulated period for dummy entry should also be 0.
> Otherwise, the total overhead could be overcounted.
> [perf]$ perf record -e '{LLC-load-misses,cpu/instructions/}'
> --call-graph=lbr ./tchain
> [perf]$ perf report --stdio
>  # To display the perf.data header info, please use
>  --header/--header-only options.
>  #
>  #
>  # Total Lost Samples: 0
>  #
>  # Samples: 21K of event 'anon group { LLC-load-misses,
> cpu/instructions/
>  }'
>  # Event count (approx.): 16313667937
>  #
>  #         Children              Self  Command      Shared Object
>  Symbol
>  # ................  ................  ...........  ................
>  ............................
>  #
>    4769.98%   0.01%     0.00%   0.01%  tchain_edit  [kernel.vmlinux]
>  [k] update_fast_timekeeper
>    4356.18%   0.01%     0.00%   0.01%  tchain_edit  [kernel.vmlinux]
>  [k] trigger_load_balance
>    3181.12%   0.01%     0.00%   0.01%  tchain_edit  [kernel.vmlinux]
>  [k] irq_work_tick
>    1592.37%   0.00%     0.00%   0.00%  tchain_edit  [kernel.vmlinux]
>  [k] cpu_needs_another_gp
> 
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
> 
> Sorry for the noise which is brought by V1.
> Changes since V1:
>  - check he->stat_acc. Because it only be available when option children is set
> 
>  tools/perf/util/hist.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> index 991a351..acba139 100644
> --- a/tools/perf/util/hist.c
> +++ b/tools/perf/util/hist.c
> @@ -2062,6 +2062,8 @@ static struct hist_entry *hists__add_dummy_entry(struct hists *hists,
>  	if (he) {
>  		memset(&he->stat, 0, sizeof(he->stat));
>  		he->hists = hists;
> +		if (he->stat_acc)
> +			memset(he->stat_acc, 0, sizeof(he->stat));

we use symbol_conf.cumulate_callchain check for existance of he->stat_acc
I think we should keep it here as well

thanks,
jirka