linux-kernel - Re: [PATCH v2 2/6] perf record: Get the first sample time and last sample time

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Date:   Wed, 27 Sep 2017 14:16:14 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v2 2/6] perf record: Get the first sample time and last
 sample time

On Tue, Sep 26, 2017 at 06:57:58PM +0800, Jin Yao wrote:
> In perf record, it's walked on all samples yet. So it's very easy to get
> the first/last samples and save the time to perf file header via the
> function write_sample_time().
> 
> In later, perf report/script will fetch the time from perf file header.
> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/builtin-record.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 9b379f3..3428633 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -80,6 +80,8 @@ struct record {
>  	bool			timestamp_filename;
>  	struct switch_output	switch_output;
>  	unsigned long long	samples;
> +	u64			first_sample_time;
> +	u64			last_sample_time;

so we have those 2 u64 already in 3 structs: evlist, session and now record

can't we do that with just in one? I'd think all of them should be available
and reachable everywhere

jirka