linux-kernel - Re: [PATCH v3 1/3] perf diff: Support --time filter option

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Date:   Tue, 5 Mar 2019 09:06:04 +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 1/3] perf diff: Support --time filter option



On 3/4/2019 11:41 PM, Jiri Olsa wrote:
> On Mon, Mar 04, 2019 at 08:52:38PM +0800, Jin Yao wrote:
>> For better support for perf diff, it would be useful to add --time filter
>> option to diff the samples within given time window.
>>
>> It supports time percent with multipe time ranges. Time string is
>> 'a%/n,b%/m,...' or 'a%-b%,c%-%d,...'.
>>
>> For example:
>>
>> Select the second 10% time slice to diff:
>> perf diff --time 10%/2
>>
>> Select from 0% to 10% time slice to diff:
>> perf diff --time 0%-10%
>>
>> Select the first and the second 10% time slices to diff:
>> perf diff --time 10%/1,10%/2
>>
>> Select from 0% to 10% and 30% to 40% slices to diff:
>> perf diff --time 0%-10%,30%-40%
>>
>> It also supports to analyze samples within given time window as:
>> <start>,<stop>. Times have the format seconds.microseconds. If start
>> is not given (i.e., time string is ',x.y') then analysis starts at
>> the beginning of the file. If stop time is not given (i.e, time
>> string is 'x.y,') then analysis goes to end of file. Time string is
>> 'a1.b1,c1.d1:a2.b2,c2.d2'. Use ':' to separate timestamps for different
>> perf.data files.
>>
>> For example, we get the timestamp information from perf script.
>>
>> perf script -i perf.data.old
>>    mgen 13940 [000]  3946.361400: ...
>>
>> perf script -i perf.data
>>    mgen 13940 [000]  3971.150589 ...
>>
>> perf diff --time 3946.361400,:3971.150589,
>>
>> It analyzes the perf.data.old from the timestamp 3946.361400 to
>> the end of perf.data.old and analyzes the perf.data from the
>> timestamp 3971.150589 to the end of perf.data.
>>
>>   v3:
>>   ---
>>   Don't parse the time string if --time option is not set.
>>   Refactor the code to make it simpler.
> 
> it's much clearer now, thanks for doing this, some nits below
> 

Thanks!

> SNIP
> 
>> +
>>   static int __cmd_diff(void)
>>   {
>>   	struct data__file *d;
>>   	int ret = -EINVAL, i;
>> +	char *abstime_ostr, *abstime_tmp;
>> +
>> +	abstime_ostr = abstime_str_dup();
>> +	abstime_tmp = abstime_ostr;
> 
> could be just one line:
> 
> 	abstime_ostr = abstime_tmp = abstime_str_dup();
> 
> also please fail if the allocation fails
> 

OK, I will fix that.

>>   
>>   	data__for_each_file(i, d) {
>> -		d->session = perf_session__new(&d->data, false, &tool);
>> +		d->session = perf_session__new(&d->data, false, &pdiff.tool);
>>   		if (!d->session) {
>>   			pr_err("Failed to open %s\n", d->data.path);
>>   			ret = -1;
>>   			goto out_delete;
>>   		}
>>   
>> +		if (pdiff.time_str) {
>> +			ret = parse_time_str(d, abstime_ostr, &abstime_tmp);
>> +			if (ret < 0)
>> +				goto out_delete;
>> +		}
>> +
>>   		ret = perf_session__process_events(d->session);
>>   		if (ret) {
>>   			pr_err("Failed to process %s\n", d->data.path);
>> @@ -791,6 +889,9 @@ static int __cmd_diff(void)
>>   		}
>>   
>>   		perf_evlist__collapse_resort(d->session->evlist);
>> +
>> +		if (pdiff.ptime_range)
>> +			zfree(&pdiff.ptime_range);
>>   	}
>>   
>>   	data_process();
>> @@ -802,6 +903,13 @@ static int __cmd_diff(void)
>>   	}
>>   
>>   	free(data__files);
>> +
>> +	if (pdiff.ptime_range)
>> +		zfree(&pdiff.ptime_range);
> 
> is this zfree needed? you free it in a loop for every data above
> 

Yes, we need this zfree. Because if we read the __cmd_diff() in 
uiltin-diff.c directly (not only read from this patch), we may see other 
"goto out_delete" cases, the zfree in loop may be not called. So we need 
an additional zfree checking in error handling.

Thanks
Jin Yao

> jirka
> 
> 
> SNIP
>