linux-kernel - Re: [PATCH v5 2/6] perf record: Get the first sample time and last sample time

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Date:   Mon, 23 Oct 2017 17:04:36 +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 v5 2/6] perf record: Get the first sample time and last
 sample time

On Sat, Oct 21, 2017 at 07:27:50AM +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.
> 
> Change log:
> -----------
> v5: There is an issue that the sample walking can only work when
>     '--buildid-all' is not enabled. So we need to let the walking
>     be able to work even if '--buildid-all' is enabled and let the
>     processing skips the dso hit marking for this case.
> 
>     At first, I want to provide a new option "--record-time-boundaries".
>     While after consideration, I think a new option is not very
>     necessary.
> 
> v3: Remove the definitions of first_sample_time and last_sample_time
>     from struct record and directly save them in perf_evlist.
> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/builtin-record.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index a6cbf16..bd711e8 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -391,8 +391,19 @@ static int process_sample_event(struct perf_tool *tool,
>  {
>  	struct record *rec = container_of(tool, struct record, tool);
>  
> -	rec->samples++;
> +	if (rec->evlist->first_sample_time == 0)
> +		rec->evlist->first_sample_time = sample->time;
> +
> +	rec->evlist->last_sample_time = sample->time;
> +
> +	/*
> +	 * If --buildid-all is given, it marks all DSO regardless of hits,
> +	 * so no need to process this sample.
> +	 */
> +	if (rec->buildid_all)
> +		return 0;
>  
> +	rec->samples++;
>  	return build_id__mark_dso_hit(tool, event, sample, evsel, machine);
>  }
>  
> @@ -415,13 +426,6 @@ static int process_buildids(struct record *rec)
>  	 */
>  	symbol_conf.ignore_vmlinux_buildid = true;
>  
> -	/*
> -	 * If --buildid-all is given, it marks all DSO regardless of hits,
> -	 * so no need to process samples.
> -	 */
> -	if (rec->buildid_all)
> -		rec->tool.sample = NULL;

hum, could you still unset the sample if there's no time given?
and keep the speed in this case..

jirka