[PD] disable cores on linux to use as dedicated dsp

[Giulio Moro]

I believe the solution to these things lies in using Xenomai or other RT extensions for Linux. With Xenomai you take control of the scheduler and you can have one process taking up an entire CPU, while the Linux kernel waits ( or uses other CPUs).
Giulio
 
      From: Jonathan Wilkes via Pd-list <pd-list at lists.iem.at>
 To: Simon Iten <itensimon at gmail.com>; Pd-List <pd-list at lists.iem.at> 
 Sent: Wednesday, 7 September 2016, 18:50
 Subject: Re: [PD] disable cores on linux to use as dedicated dsp
   
> On Wednesday, September 7, 2016 12:51 PM, Simon Iten <itensimon at gmail.com> wrote:

> hi list,

> i recorded 3 times in a studio last year that uses a daw/pc 
> interconnection by pyramix, basically it is a hacked windows system, 
> where one or two cores of a multicore cpu are completely hidden from the 
> system. these cores are then acessed directly by the daw and used as a 
> very powerful dsp. the system is incredible! lowest latencies, high 
> trackcount, and the breakout to the adc/dac is a simple network cable.

> see here for additional info:

> http://www.merging.ch/products/pyramix/masscore

> i since wondered if this would be a way to go for puredata? at least on 
> linux it seems very easy to deactivate a core (but i don't know if it 
> than can be used directly by a process) : echo 0 > 
> /sys/devices/system/cpu/cpu1/online for core2 for example.


> is this a completely stupid idea? note that i have no idea how hard it 
> would be to implement something like this


> thanks for any insight


Hi Simon,
That quite an intriguing design.

It hurts my brain too much to try to assess the difficulty of such an undertaking to 
refactor Pure Data to this design.  
So let me try a shortcut:

Inside d_ugen.c (which is essentially just dsp algos, so there should be few if any 
system calls) I see a t_getbytes call.  t_getbytes calls calloc.

With the design you linked to, do Pd devs have to reimplement malloc?  If the answer 
is yes, then I'd call this a massively difficult undertaking.  If d_* relies on the 
system calls, then you can bet x_*, m_*, s_*, and g_* do, too, and to a much greater 
extent.

If the answer is no, I'd like to learn more about the design.

-Jonathan

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