linux-kernel - Re: [PATCH v7 2/6] perf record: Get the first sample time and last sample time

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Date:   Thu, 4 Jan 2018 16:09:03 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     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 v7 2/6] perf record: Get the first sample time and last
 sample time

Em Fri, Dec 08, 2017 at 09:13:42PM +0800, Jin Yao escreveu:
> In the default 'perf record' configuration, all samples are processed,
> to create the HEADER_BUILD_ID table. 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().
> 
> Later, at post processing time, perf report/script will fetch
> the time from perf file header.

So, at this point I was expecting that that record would be present on
the perf.data file:

[acme@...et perf]$ perf record --timestamp-boundary sleep 1
Cannot read kernel map
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data (7 samples) ]
[acme@...et perf]$ perf report -D | grep PERF_RECORD_SAMPLE | wc -l
7
[acme@...et perf]$ perf report -D | grep PERF_RECORD_SAMPLE_TIME
[acme@...et perf]$

What am I doing wrong?

To clarify, this is with just the first two patches in this series
applied.

- Arnaldo
 
> Change log:
> -----------
> v7: Just update the patch description according to Arnaldo's suggestion.
> 
> v6: Currently '--buildid-all' is not enabled at default. So the walking
>     on all samples is the default operation. There is no big overhead
>     to calculate the timestamp boundary in process_sample_event handler
>     once we already go through all samples. So the timestamp boundary
>     calculation is enabled by default when '--buildid-all' is not enabled.
> 
>     While if '--buildid-all' is enabled, we creates a new option
>     "--timestamp-boundary" for user to decide if it enables the
>     timestamp boundary calculation.
> 
> 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/Documentation/perf-record.txt |  3 +++
>  tools/perf/builtin-record.c              | 18 +++++++++++++++---
>  2 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 5a626ef..3eea6de 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -430,6 +430,9 @@ Configure all used events to run in user space.
>  --timestamp-filename
>  Append timestamp to output file name.
>  
> +--timestamp-boundary::
> +Record timestamp boundary (time of first/last samples).
> +
>  --switch-output[=mode]::
>  Generate multiple perf.data files, timestamp prefixed, switching to a new one
>  based on 'mode' value:
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 98da8cb..6db7b5a 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -78,6 +78,7 @@ struct record {
>  	bool			no_buildid_cache_set;
>  	bool			buildid_all;
>  	bool			timestamp_filename;
> +	bool			timestamp_boundary;
>  	struct switch_output	switch_output;
>  	unsigned long long	samples;
>  };
> @@ -409,8 +410,15 @@ 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 (rec->buildid_all)
> +		return 0;
> +
> +	rec->samples++;
>  	return build_id__mark_dso_hit(tool, event, sample, evsel, machine);
>  }
>  
> @@ -435,9 +443,11 @@ static int process_buildids(struct record *rec)
>  
>  	/*
>  	 * If --buildid-all is given, it marks all DSO regardless of hits,
> -	 * so no need to process samples.
> +	 * so no need to process samples. But if timestamp_boundary is enabled,
> +	 * it still needs to walk on all samples to get the timestamps of
> +	 * first/last samples.
>  	 */
> -	if (rec->buildid_all)
> +	if (rec->buildid_all && !rec->timestamp_boundary)
>  		rec->tool.sample = NULL;
>  
>  	return perf_session__process_events(session);
> @@ -1621,6 +1631,8 @@ static struct option __record_options[] = {
>  		    "Record build-id of all DSOs regardless of hits"),
>  	OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
>  		    "append timestamp to output filename"),
> +	OPT_BOOLEAN(0, "timestamp-boundary", &record.timestamp_boundary,
> +		    "Record timestamp boundary (time of first/last samples)"),
>  	OPT_STRING_OPTARG_SET(0, "switch-output", &record.switch_output.str,
>  			  &record.switch_output.set, "signal,size,time",
>  			  "Switch output when receive SIGUSR2 or cross size,time threshold",
> -- 
> 2.7.4