linux-kernel - Re: [PATCH v3 1/6] perf header: Record first sample time and last sample time in perf file header

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Date:   Mon, 2 Oct 2017 20:52:59 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.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 v3 1/6] perf header: Record first sample time and last
 sample time in perf file header



On 10/2/2017 7:50 PM, Jiri Olsa wrote:
> On Thu, Sep 28, 2017 at 08:45:16PM +0800, Jin Yao wrote:
> 
> SNIP
> 
>> +		return ret;
>> +
>> +	return do_write(ff, &evlist->last_sample_time,
>> +			sizeof(evlist->last_sample_time));
>> +}
>> +
>>  static void print_hostname(struct feat_fd *ff, FILE *fp)
>>  {
>>  	fprintf(fp, "# hostname : %s\n", ff->ph->env.hostname);
>> @@ -1506,6 +1520,19 @@ static void print_group_desc(struct feat_fd *ff, FILE *fp)
>>  	}
>>  }
>>  
>> +static void print_sample_time(struct feat_fd *ff, FILE *fp)
>> +{
>> +	struct perf_session *session;
>> +
>> +	session = container_of(ff->ph, struct perf_session, header);
>> +
>> +	fprintf(fp, "# time of first sample : %" PRIu64 "\n",
>> +		session->evlist->first_sample_time);
>> +
>> +	fprintf(fp, "# time of last sample : %" PRIu64 "\n",
>> +		session->evlist->last_sample_time);
> 
> this could be done in some follow up patch, but could we
> display this in some human readable way.. 
> 
> # time of first sample : 218077073264620
> # time of last sample : 218077073395488
> 
> jirka
> 

Could I add the printing of duration? For example,

duration = (double)(last_sample_time - first_sample_time) / NSEC_PER_MSEC;
fprintf(fp, "# sample duration: %10.3f (ms)\n", duration);

fprintf(fp, "# time of first sample : %" PRIu64 "\n",
        first_sample_time);

fprintf(fp, "# time of last sample : %" PRIu64 "\n",
        last_sample_time);

Thanks
Jin Yao