Cadence Debian RT Kernel

[AnthonyCFox]

I switched to a Debian-based distro (SolydK) and discovered that, hidden right under my nose in the Debian repo, is a PREEMPT_RT patched kernel http://packages.debian.org/jessie/linux ... rt-686-pae available for Wheezy, Jessie and Sid.

I see that in Cadence, under System Checks/Current Kernel, there's no check mark or any indication the kernel is realtime. This kernel is, what I think it is, isn't it? Is it just that the name isn't formatted the way Cadence expects, or something minor like that?

EDIT: While it does have the preempt patch, the system timer isn't set to 1000 hz, and it doesn't support the tickless timer. Not quite the desired kernel for audio production.

RE-EDIT: Then again, maybe that stuff doesn't even matter.

[AnthonyCFox]

Great. I figured that was the case.

I mostly wanted to post this because there aren't a lot of links pointing to the fact that Debian has a realtime kernel in their repositories. So, hey Google! Send people looking for debian realtime kernel, debian lowlatency kernel, here! Mint Debian Edition, LMDE, Linux BBQ, SolydX, SolydKX, debian stable, debian testing, debian unstable

[skavar]

Great. I figured that was the case.

I mostly wanted to post this because there aren't a lot of links pointing to the fact that Debian has a realtime kernel in their repositories. So, hey Google! Send people looking for debian realtime kernel, debian lowlatency kernel, here! Mint Debian Edition, LMDE, Linux BBQ, SolydX, SolydKX, debian stable, debian testing, debian unstable

Yeah, its so cool to have the latest kernel with real time patches right there in the Debian repositories... one click and there it is, installed.
Playing well with the AMD video drivers also.

[AnthonyCFox]

Great.

So, it's not exactly the desired kernel.

It does have the preempt patch, but system timer isn't set to 1000 hz, and it doesn't support the tickless timer. Important stuff.

[raboof]

I noticed that, too - I wonder whether there's a reason for that (i.e. I'm not completely sure whether the timer clock still matters, and what the difference is between NO_HZ/NO_HZ_FULL/NO_HZ_COMMON/NO_HZ_IDLE). Perhaps open a bug report to ask them about it? Or can we find a better means of communication?

[AnthonyCFox]

I noticed that, too - I wonder whether there's a reason for that (i.e. I'm not completely sure whether the timer clock still matters, and what the difference is between NO_HZ/NO_HZ_FULL/NO_HZ_COMMON/NO_HZ_IDLE). Perhaps open a bug report to ask them about it? Or can we find a better means of communication?

Dude, I'm using your realtimeconfigquickscan script. If you don't know, I sure as heck don't.

Probably should figure out if it matters before filing a bug report. Who can figure that out? I can eyeball it, when I finish getting everything set up and get back to my project. But, that will be comparing SolydK with debian's rt patched kernel to Arch with Liquorix's patches compiled on my machine. If it's in the same ballpark, I'll be satisfied; but it's hardly "proof".

[AnthonyCFox]

For what it's worth, I asked about this on Linux BBQ forums (it's the bleeding edge of Debian) http://linuxbbq.org/bbs/viewtopic.php?f=6&t=961#p16811 and this was the response:

Hi,

from what I know, a 'simple' rt kernel does the job well - there was a discussion on about whether the refinements are needed, and it seems that there are other factors that are more important to guarantee a low latency. Please see the info here, at the bottom: http://linuxbbq.org/wiki/index.php?title=Rocks!

So, IMO, these 'two things' are not really making a difference if you create an environment that has no unnecessary service running, like network and USB devices that create jitter.

And here's the relevant (IMO) information from the page he linked to:

Please try to use PS/2 mice and keyboard whenever possible if you work with RT kernels. The CPU governor should be switched to 'performance' mode. Disable power management, screensaver, and turn off unwanted background processes. It is recommended to switch off network (disable network services) or put them down in priority (Remember: RTPRIO can be as high as 99 opposed to Nice values between -20 and +19, and RT priorities will always be above Nice priorities. Use 'ps -eu pid,rtprio,cmd' to list the processes and their RT priority values)

I guess the advice to give people would be, "Do what you can, and if it works don't sweat the rest." And, trust your ears, that's all that really matters.

[AnthonyCFox]

Liquorix is another option. It doesn't have the preempt_rt patch or support tickless timer but the system timer is set to 1000hz.

Here's how to get it:

# /etc/apt/sources.list.d/liquorix.list
deb http://liquorix.net/debian sid main

All packages in the liquorix repository are signed. Run the command below to install all the keyring packages for liquorix.net.

sudo apt-get install '^liquorix-([^-]+-)?keyring.?'

Thanks to the BBQ forums for this http://linuxbbq.org/bbs/viewtopic.php?f ... 857#p16856

I'm just going to run this one for awhile and see how it goes, then maybe I'll switch back to the preempt_rt kernel in a few weeks and compare.

[juki]

you can use the real time kernel from Tango Studio repositories.

http://download.tuxfamily.org/tangostud ... n/l/linux/

[AnthonyCFox]

you can use the real time kernel from Tango Studio repositories.

http://download.tuxfamily.org/tangostud ... n/l/linux/

That is good for people running Wheezy.

I'm more focused on modern OS's.

[AnthonyCFox]

I also asked about the Siduction kernel and here's the response: http://forum.siduction.org/index.php?to ... 8#msg35418

siduction has CONFIG_HZ=1000 and CONFIG_NO_HZ=y but not RT patch. I have seen several reports on LAU list that audio performance is quite good anyway.

Maybe a better option than Liquorix. Better than the rt kernel in the Debian repos? *shrugs*

Hey, at least there are options!

[stanlea]

you can use the real time kernel from Tango Studio repositories.

http://download.tuxfamily.org/tangostud ... n/l/linux/

That is good for people running Wheezy.

I'm more focused on modern OS's.

Are you considering that Wheezy is not modern, or Debian in general ? Actually I use Wheezy, but I look froward to use Jessie, more up to date. Just hoping that the KX repos will work.

[AnthonyCFox]

Are you considering that Wheezy is not modern, or Debian in general ?

I'm just teasing. Wheezy is getting pretty long in the tooth. I thought they said they were going to speed up the release cycle a bit? I find it amazing that after all these years Debian is on their seventh release. But hey, for anyone looking for a stable OS, Debian is the definition of stable.

Actually I use Wheezy, but I look froward to use Jessie, more up to date. Just hoping that the KX repos will work.

I'm using the KX repos with SolydK, which is based on Jessie, and I'm a happy camper.