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

["Jin, Yao" <yao.jin@linux.intel.com>]

On 10/2/2017 9:00 PM, Jiri Olsa wrote:
> On Mon, Oct 02, 2017 at 08:52:59PM +0800, Jin, Yao wrote:
>>
>>
>> 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);
> 
> could be, but mainly please display the time same way the perf script does:
> 
>   218482.819815
> 
> jirka
> 

Fine. I think I can use timestamp__scnprintf_usec() to print the timestamp. 

BTW, do we need the duration printing here?

Thanks
Jin Yao