linux-kernel - Re: [PATCH v6 2/6] perf record: Get the first sample time and last sample time

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Date:   Wed, 22 Nov 2017 09:09:21 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
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 v6 2/6] perf record: Get the first sample time and last
 sample time



On 11/22/2017 12:40 AM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Nov 06, 2017 at 08:21:07PM +0800, Jin Yao escreveu:
>> In perf record, it's walked on all samples yet. So it's very easy to get
> 
> "In the default 'perf record' configuration, all samples are processed,
> to create the HEADER_BUILD_ID table. So..."
> 
>> 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.
> 
>    Later, at post processing time, ...
> 

Thanks Arnaldo! The update on patch description is good.

>>
>> Change log:
>> -----------
>> v6: Currently '--buildid-all' is not enabled at default. So the walking
> 
>                  --no-buildid-all, right?
>

No, it is '--buildid-all'. There is no '--no-buildid-all' available now.

See in __record_options[] (builtin-record.c),

	OPT_BOOLEAN(0, "buildid-all", &record.buildid_all,
	    	"Record build-id of all DSOs regardless of hits"),

So by default, buildid-all is set with false.

Thanks
Jin Yao

>>      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 f4d9fc5..082a0cb 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;
>>   };
>> @@ -391,8 +392,15 @@ 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);
>>   }
>>   
>> @@ -417,9 +425,11 @@ 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);
>> @@ -1579,6 +1589,8 @@ 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