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

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

[taeung]

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 ?

Thanks,
Taeung

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

[Namhyung Kim]

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? :)

Thanks,
Namhyung

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

[taeung]

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

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

[TaeWoong Song]

Hi,

I sent patch file about a visual cue for toggle zeroing of samples in pert top.

To know whether it is with -z option in a function hists__browser_title(), 
I add a argument 'struct hist_browser_timer *hbt' in the function.

The cause is 'hbt' can get current value of 'pert_top.zero' and know whether it is 'report' or 'top'.

Does it look good ? 

Thanks,
Taeung
On Oct 1, 2014, at 10:45 AM, taeung <treeze.taeung@gmail.com> wrote:

> 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.
>