2010/6/30 András Murányi <muranyia@gmail.com>

The point is that the newest kernel versions are not available in rt flavour (the latest is 2.6.31-11 and my experiences were not good with it). This is first time i heard about the lowlatency flavour, but it's not in my Ubuntu repos.
So i'm afraid, if i want a new rt kernel (for 64-bit...), i'll have to use a ppa or build my own.

Andras
2010/6/30 Pedro Lopes <pedro.lopes@ist.utl.pt>
What?

Of course not. Its a pacth - no compiling needed. But be sure to keep a generic kernel at the boot (just use grub to preserve a boot without rt, I never had problems and use the same rt kernel for 1 year, but safety first =P)

Real time (-rt) and Low latency (-lowlatency) kernels

You may want to install the -lowlatency kernel, you can simply do:
 sudo apt-get install linux-lowlatency linux-headers-lowlatency
If you still experience Xruns or you have a firewire sound card supported by the FFADO project, you may want to install the -rt kernel:
 sudo apt-get install linux-rt linux-headers-rt
2010/6/30 András Murányi <muranyia@gmail.com>

Buh, it seems then i'll need to get a kernel from a PPA or compile it myself. A bit afraid of it, honestly.
Thanks for the explanation!

Andras

On Sat, Jun 26, 2010 at 12:50 PM, Ricardo Lameiro <ricardolameiro@gmail.com> wrote:

well, AFAIK, the "RT" Kernel is a generic kernel that is modified by a special patch, that is made by Ingo Molnár. This patch gives the kernel the ability to have a behavior that allows the assignment of time frames and allocations to compute "rt" flagged tasks. Maybe this could be translated to the scheduler.In the other hand, the preemptive kernel, its a normal Generic kernel, that its compiled with different options. At compile time, the configuration of the scheduler and company are configured more aggressively to give a better response to the "rt" flagged apps.

As my opinion, that is worth nothing...., the preemptive kernels are comming into a very good level, since the main tree ot the generic kernel, has absorbing parts of Ingo's patches. But, still, the RT kernel is way more accurate on the scheduling etc. problem is that, RT kernels are in nature more Power hungry, and by the nature of its working, they could hang easily a computer, keeping only processing an high prio task.

If I said something wrong, please correct me, I have looked at this stuff since a year to try to understand it better, so if someone can explain it better, please do.

Ricardo Lameiro

2010/6/26 Andre "Osku" Schmidt <andre.osku.schmidt@osku.de>

On Fri, 2010-06-25 at 22:17 +0200, András Murányi wrote:
> Hello people,
>
> does anyone know what is the real difference between an 'rt' and a
> 'preempt' kernel in linux?

dunno, but here's a pretty interesting talk about real-time kernel
http://lac.linuxaudio.org/2010/recordings/day2_1045_How_the_Real_Time_Kernel_Helps_Audio_and_Video_Applications.ogv
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