Re: Linux 6.12 new preemption models

[kiasoc5 <kiasoc5@disroot.org>]

On 1/1/25 17:51, Leo Famulari wrote:
> FYI, Linux / linux-libre 6.12 introduces a new set of preemption
> options:
> 
> ------
> Preemption Model
>    1. No Forced Preemption (Server) (PREEMPT_NONE)
>> 2. Voluntary Kernel Preemption (Desktop) (PREEMPT_VOLUNTARY)
>    3. Preemptible Kernel (Low-Latency Desktop) (PREEMPT)
>    4. Fully Preemptible Kernel (Real-Time) (PREEMPT_RT) (NEW)
> ------
> 
> These options trade between kernel throughput and latency.
> 
> PREEMPT_NONE is how the kernels worked before 6.12.
> 
> The trade-off made in PREEMPT_VOLUNTARY is suggested for desktops, so
> I'm going to select it for our 6.12 kernel packaging and it will
> presumably remain so for future versions as well.
> 
> But if you are building Guix kernels for a busy server or HPC, you
> should select PREEMPT_NONE. And you might have use cases for the other
> options as well.
> 
> Let me know if you disagree.
> 
> References:
> https://cateee.net/lkddb/web-lkddb/PREEMPT_NONE.html
> https://cateee.net/lkddb/web-lkddb/PREEMPT_VOLUNTARY.html
> https://cateee.net/lkddb/web-lkddb/PREEMPT.html
> https://cateee.net/lkddb/web-lkddb/PREEMPT_RT.html
> 


How about PREEMPT_DYNAMIC: 
https://cateee.net/lkddb/web-lkddb/PREEMPT_DYNAMIC.html

This enables changing between PREEMPT_NONE, PREEMPT_VOLUNTARY, and 
PREEMPT at boot time. Then the only kernel that needs to be compiled 
separate is PREEMPT_RT.