[LAU] Freebob high CPU usage

[Pieter Palmers]

Hector Centeno wrote:
> Thanks for your responses,
> 
> I was comparing same latency settings, but it's true, it's unfair to
> compare a two channel interface with a 10+midi one.
Nevertheless the CPU usage of freebob/ffado is higher than that of usb 
devices.

> 
> Pieter: I'm using jack and freebob from the Ubuntu repositories
> (libfreebob0 version 1.0.7-1). Is that a debug build?

Probably not.

Greets,

Pieter

> 
> Regards,
> 
> Hector
> 
> 
> On Sun, Sep 21, 2008 at 5:24 AM, Pieter Palmers <pieterp at joow.be> wrote:
>> hollunder at gmx.at wrote:
>>> On Sun, 21 Sep 2008 01:06:21 -0400
>>> "Hector Centeno" <hcengar at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> I have two computers (desktop and laptop) with Ubuntu Hardy (using
>>>> kernel RT on both) and a Edirol FA-101 firewire interface. I was
>>>> comparing Jack's CPU usage (no other audio app running) using the
>>>> Edirol against a USB M-Audio Transit. I noticed on both computer the
>>>> CPU usage to be much higher with the firewire interface than with the
>>>> USB. On my laptop goes up to 15% or more and 8% on my desktop
>>>> (Centrino Duo @ 1.7GHz and Core 2 Duo @ 2.1 GHz respectively) while
>>>> using the USB interface the usage remains below 1%. Is this a normal
>>>> behaviour of firewire interfaces? Is this a Jack related issue? Is
>>>> there a recent and more efficient version of Freebob (ffado maybe?)
>>>> than the one from the Ubuntu repos?
>>>>
>>>> Cheers,
>>>>
>>>> Hector
>>> Are you sure that you are comparing the same latency settings? Just
>>> a thought because Firewire is capable of lower latencies than USB and
>>> lower latencies also mean higher cpu usage.
>>> As said, just a thought, I never used FW.
>> This is partially true.
>>
>> The fact that the transit has only a channel count of 2in/4out while the
>> FA-101 has 10in/10out + midi makes that it's not really a fair comparison.
>>
>> However the main issue is that the kernel-space firewire implementation
>> is not very CPU efficient. There are some issues with how DMA memory
>> coherence is implemented that make things CPU intensive. Messing with
>> the kernel level implementation to improve CPU consumption is not
>> considered a priority for the freebob/ffado developers ATM. The 'new'
>> firewire kernel drivers will allow us to implement a more efficient
>> scheme reducing CPU. But let's first get the current FFADO out.
>>
>> FreeBoB/FFADO themselves are fairly CPU efficient, although things can
>> always be improved.
>>
>> Greets,
>>
>> Pieter
>>
>> PS: you don't by any chance use a freebob/ffado debug build?
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>