Re: [Jack-Devel] jack dsp load calculation

On 12/26/2015 02:33 PM, Kjetil Matheussen wrote:
> On Sat, Dec 26, 2015 at 1:56 PM, Robin Gareus <[hidden]> wrote:
> 
>> On 12/23/2015 09:20 PM, John Emmas wrote:
>>> On 23 Dec 2015, at 15:35, Robin Gareus wrote:
>>>
>>>> Hi all,
>>>>
>>>> I'd like to propose changing the algorithm how jack calculates the DSP
>>>> load from averaging to worst-case.
>>>>
>>>> The main reason for having DSP load is to know how much more processing
>>>> one can safely add without getting x-runs. What matters in this case is
>>>> the worst-case value.
>>>>
>>>
>>> Matters to whom..?
>>
>> Those who want to know the peak DSP load and available headroom.
>>
>> The average is meaningless in the context of DSP. A system may run
>> without x-runs 99% of the time but then some NMI or SMI comes along and
>> ruins it all. Nobody cares if the average is below 50%.
>>
>>
> For what it's worth, Radium reports three values: 1. Minimum CPU measured
> for a block during the last second, 2. Average CPU usage during the last
> second,
> 3. Maximum CPU usage measured for a block during the last second
> ( http://folk.uio.no/ksvalast/radiumcpu.png )

nice.

That is per application, right?  Not the whole system - jack can include
other clients.

> All three values are useful, at least for me as a developer of the program,
> but I guess the users might find all three values interesting as well. 

For end users in Mixbus  we are considering to maybe even "dumb it
down": A simple light: green/yellow/red or a short e.g 6-LED peak-meter.

The motivation here: don't encourage comparing percent values.

However it must be meaningful to answer
 1) can I safely add more plugins?
 2) can I lower the period-size or is the current cycle already very
short for my setup?

> At least
> the user doesn't have to wonder whether it's showing peak or average
> values, and what the average/peak values would have been if only one
> of them had been shown. I guess peak value is the most useful value,
> but by showing average and minimum as well, we also indicate the potential
> performance the program can deliver without xruns. This potential
> can be used by the user to close other programs and do other operations
> that might make the computer perform better.
> 
> One thing I'm not quite sure of, which is always apparent because all the
> values are visible, is why there is such a large difference between
> minimum and maximum CPU usage. It's usually at least 4-10
> percentage points. I hope it's because of measurement
> errors.

On which platform is that? with JACK?

best,
robin

1451138678.28703_0.ltw:2,a <567E9E6B.8010500 at gareus dot org>