Re: [Linux PPC] Disable PREEMPT

On Wed, Feb 25, 2026 at 08:16:46AM +0100, Christophe Leroy (CS GROUP) wrote:

+Peter

Hi Christian,

Le 25/02/2026 à 06:54, Christian Zigotzky a écrit :

quoted

Hello,

We were previously able to disable PREEMPT in the kernel configuration,
but the latest kernels now enable it by default and it is no longer
possible to disable it.

Is it possible to let us decide whether to activate PREEMPT or not?

Can you give more details on why you want to be able to deactivate PREEMPT ?

Read https://github.com/torvalds/linux/commit/7dadeaa6e851e

Right. So to recap, there are and will be more cases where relying on
preemption is mandatory. 

The typical example is huge page memset/memcpy. Currently that is done
in single page chunks with cond_resched() in between, but it is much
better (and faster) to do a full huge page in one go.

Combine this with the endless stream of mostly random cond_resched()
placements due to $reason, and it is all a bit of a maintenance
nightmare.

I suppose the question is; why do you think you require non-preempt
kernels?