Re: What do zeroing of samples in 'perf top' mean ?

[taeung <treeze.taeung@gmail.com>]

Thanks for your answer.

On 09/30/2014 02:55 PM, Namhyung Kim wrote:
> Hi Taeung,
>
> On Tue, 30 Sep 2014 12:19:41 +0900, taeung wrote:
>> Hi,
>>
>> I have two questions about 'zeroing of samples' in 'perf top'.
>>
>> I knew if I use 'perf top', I can see a performance counter profile in
>> real time.
>> But I can't find a difference between 'perf top -a' and 'perf top 
>> --zero'.
>>
>> After 'perf top' is run , I press key 'z' to toggle zeroing of samples.
>> But I don't know a difference between when I press key 'z' and before
>> I did it.
>>
>> 1. What is 'Zero history' ?
>> (I saw it in Documentation/perf-top.txt that '--zero' option is 'Zero
>> history across display updates.')
>>
>> 2. What do 'zeroing of samples' mean ?
> It seems that both questions are same.
>
> The way perf top works is collecting samples and cumulate them into the
> history (with decaying).  So it basically shows current value + old
> value.  With -z option, it won't use old values.
>
> And yes, one cannot easily find a difference between -z option and
> normal output.  So we might need a visual cue as Arnaldo suggested
> earlier.  Are you interested in implementing it?
Yes , I really wanna implement it
to easily find a difference between -z option and default option.

At last, I understand what -z option mean.

As what Arnaldo suggested , I'll implement it.

Thanks,
Taeung