Maintaining a Real Time Stable Kernel

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rncbc
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Re: Maintaining a Real Time Stable Kernel

Postby rncbc » Sat Aug 03, 2019 9:34 pm

actually jackdmp aka jackd2 uses multiple threads/cores *iif* the jack graph takes 'parallel' paths; iow: jack clients that are connected consecutively do always use one and only logical thread/core (might migrate across the several available but that's purely os/kernel/cpu scheduler business, not jack's).

qtractor (and also ardour ofc. when set as a jack client): as one single jack client, all pure-DSP/real-time processing will only use one jack-thread/core (the real-time one), no matter what; however, due to their multi-threaded architecture, most non-real-time processing, which includes many several other tasks than just the GUI event-loop for that matter, will take and will be scheduled to run on any other core/thread and none of that related to the "multi-processing" feature of jackdmp/jackd2, whatever.

so whether being called a DAW, or not, is not the point here ;) jackdmp/jackd2 will only take use of more than one core if and only if you have split graph paths.

eg. assuming A, B, C and D are different jack client instances:

1. all clients will run on same core/thread (1 thread/core);

Code: Select all

A --> B --> C --> D

2. all clients *but C* will run on same core/thread (2 thread/cores);

Code: Select all

A -.-> B -+-> D
   '-> C -'


hope to have made it clear now.
cheers

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khz
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Re: Maintaining a Real Time Stable Kernel

Postby khz » Sun Aug 04, 2019 6:37 am

Thanks rncbc.
If this has something to do with it, how does irqbalance (viewtopic.php?p=108966#p108966) relate to audio processing? Is that (still) important?
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tramp
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Re: Maintaining a Real Time Stable Kernel

Postby tramp » Sun Aug 04, 2019 7:10 am

rncbc wrote:so whether being called a DAW, or not, is not the point here ;) jackdmp/jackd2 will only take use of more than one core if and only if you have split graph paths.


Exact, and that was my point here, Ardour does that, you'll find a rt-thread for any track you create in ardour, so, parallel processing is possible when use jackd2.

My stance about qtractor being a DAW or not, was just a joke, for me, it is. :D
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bluebell
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Re: Maintaining a Real Time Stable Kernel

Postby bluebell » Sun Aug 04, 2019 10:52 am

Coming soon:

q.png
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rncbc
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Re: Maintaining a Real Time Stable Kernel

Postby rncbc » Sun Aug 04, 2019 5:26 pm

tramp wrote:Ardour does that, you'll find a rt-thread for any track you create in ardour, so, parallel processing is possible when use jackd2.

my point is that so called Ardour's rt-thread per track are NOT the same as the jackdmp/jackd2 process cycle real-time thread(s), precisely the ones that make up for its multi-processing/core magic ;)

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Re: Maintaining a Real Time Stable Kernel

Postby tramp » Sun Aug 04, 2019 9:01 pm

True, but nuitpicking. The result is the same.
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Re: Maintaining a Real Time Stable Kernel

Postby bluebell » Mon Aug 05, 2019 10:12 am

tramp wrote:True, but nuitpicking. The result is the same.


Is it? Can Ardour saturate several CPU cores by just using several tracks with CPU-hungry plugins, for example 32 tracks with a CALF multiband limiter in 4x oversampling mode in each track?
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Re: Maintaining a Real Time Stable Kernel

Postby tramp » Mon Aug 05, 2019 1:48 pm

It is. The magic to Split the dsp over several cores is done in jackdmp, but the bare boone requirment therefor is, well, multiple callbacks.
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Re: Maintaining a Real Time Stable Kernel

Postby merlyn » Mon Aug 05, 2019 2:25 pm

I saw this post on the Ardour forum :

Maximum cores ardour can utilize

Paul Davis wrote:The parallelism relies on you having as many (or more) tracks as you do CPU cores. They also need to be independent (i.e. Track 1 does not feed Track 2). Under those circumstances (which are quite typical), you would get full utilization.

However, note that Ardour sessions with 100+ tracks run relatively easily on a 4 core system unless all the tracks are heavily burdened by CPU intensive DSP (like Reverbs and certain kinds of EQ), or digital synthesis.

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Re: Maintaining a Real Time Stable Kernel

Postby khz » Thu Aug 08, 2019 7:47 am

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Re: Maintaining a Real Time Stable Kernel

Postby bluebell » Thu Aug 08, 2019 10:39 am



Good news. The simpler it is for distributors and users to enable a RT kernel the more non-nerdy users will see the power of Linux for musicians and audio workers. Without iLok and phone-home malware (aka "installers" and "license managers").
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Re: Maintaining a Real Time Stable Kernel

Postby khz » Wed Aug 28, 2019 11:57 am

Is Nvidia improving?

Nvidia is opening up a bit: The company has recently released details on programming current generations of graphics chips under an open source license on Github.https://github.com/nvidia/open-gpu-doc This makes the work of open source developers easier, even if important information has yet to follow. https://www.phoronix.com/scan.php?page=news_item&px=NVIDIA-Open-GPU-Docs

So far, Nvidia has had a rather bad reputation with open source developers. No wonder, because unlike AMD and Intel, the company does not drive open source Linux drivers for its PC graphics chips itself. The company also helps only insignificantly and has so far handled driver programming details like state secrets. Linux developers therefore have to work a lot with reverse engineering, which is one of the main reasons why the "Nouveau" kernel and OpenGL drivers, which are standard in distributions, have many weaknesses; for example, they only loosen up part of the 3D performance and by no means support all the functions of GeForce chips.

Ultimately, however, more is needed before this problematic situation can improve significantly. For proper open source drivers, it would also be important to finally provide Linux distributors with better firmware: The one currently provided by Nvidia is more of a crutch, because it can't switch graphics chips into the most economical or fastest operating modes. This is currently the main reason why the power consumption of many modern GeForce GPUs with the Nouveau driver is often higher than with the proprietary driver, but the 3D performance is significantly worse at the same time.

Source: Linux 5.3: Netfilter Offloading and Shot before Nvidia's Bug Update (last modified 28.08.2019) https://www.heise.de/ct/artikel/Linux-5-3-Netfilter-Offloading-und-Schuss-vor-Nvidias-Bug-4470638.html
(Linus Torvalds - Nvidia F_ck You! https://www.youtube.com/watch?v=IVpOyKCNZYw ;-))

Page 2: Other highlights of Linux 5.3

Support for AMD's new graphics chip architecture is one of the highlights of Linux 5.3. The kernel version expected on September 9 or 16 will also pave the way for real-time support in Linux. The main development branch of the kernel includes a change https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a50a3f4b6a313dc76912bd4ad3b8b4f4b479c801 with https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=70e6e1b971e46f5c1c2d72217ba62401a2edc22b a new kernel configuration option that will eventually allow you to build a Fully Preemptible Kernel (Real-Time/RT). Such kernels can meet real-time requirements - guaranteeing that certain tasks can be completed within a pre-defined period of time, even under adverse conditions.
Adaptation with signal effect

The changes with the CONFIG_PREEMPT_RT configuration option give the impression that the real-time Linux patch collection PREEMPT_RT, developed almost fifteen years ago https://wiki.linuxfoundation.org/realtime/start, has finally moved into the official kernel. Many adaptations developed in this "RT-Tree" have already moved to Linux in recent years. Now follows the configuration option - many other things that are important for modern real-time operation, but remain in the RT-Tree for the time being.
c't/Thorsten Leemhuis

The configuration option does not show up at all for the time being. It signals to the world that Torvalds & Co. will soon be integrating the real-time patches remaining in the RT tree, even though Torvalds was initially rather sceptical about the idea. This is intended to motivate kernel developers who are not interested in real-time patches not to get in the way of reviewing and integrating any remaining real-time changes to the RT tree. There aren't that many of them anymore, but some concern the central and therefore critical infrastructure of the Linux kernel, where the developers take special care.

Maybe patches for 5.3 will follow, which still show the configuration option. However, it remains uncertain how long the integration of the remaining adaptations in the RT tree will take (Real Time is Coming to Linux; What Does that Mean to You? - Steven Rostedt, VMware https://www.youtube.com/watch?v=BxJm-Ujipcg); its developers last autumn had set themselves the goal of transferring everything essential to the official Linux kernel in 2019. However, the time remaining for this is slowly running out.

Image
The new option for building a real-time kernel has not yet been shown, because it should have one thing above all else: Signal effect. (Picture: c't/Thorsten Leemhuis)

Source: Linux 5.3: Netfilter Offloading and Shot before Nvidia's Bug Update (last modified 28.08.2019) https://www.heise.de/ct/artikel/Linux-5-3-Netfilter-Offloading-und-Schuss-vor-Nvidias-Bug-4470638.html?seite=2

# Artificial intelligence for languages DeepL develops artificial intelligence for understanding and translating texts. https://www.deepl.com/translator
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khz
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Re: Maintaining a Real Time Stable Kernel

Postby khz » Fri Sep 13, 2019 12:16 pm

FZ - Does humor belongs in Music?
GNU/LINUX@AUDIO ~ /Wiki $ Howto.Info && GNU/Linux Debian installing >> Linux Audio Workstation LAW
    I don't care about the freedom of speech because I have nothing to say.

GuntherT
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Re: Maintaining a Real Time Stable Kernel

Postby GuntherT » Sat Sep 14, 2019 6:25 am

khz wrote:# !vote KLANG — Kernel Level Audio Next Generation" http://klang.eudyptula.org/

LOL!

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bluebell
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Re: Maintaining a Real Time Stable Kernel

Postby bluebell » Sat Sep 14, 2019 6:50 am

GuntherT wrote:
khz wrote:# !vote KLANG — Kernel Level Audio Next Generation" http://klang.eudyptula.org/

LOL!


Audio processing in the kernel would mean plugins also running in kernel space. Cool.

What can possibly go wrong?
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