Re: [PATCH 1/9] slub: Make PREEMPT_RT support less convoluted

[Christoph Lameter]

On Wed, 17 Aug 2022, Sebastian Andrzej Siewior wrote:

> + *   On PREEMPT_RT, the local lock neither disables interrupts nor preemption
> + *   which means the lockless fastpath cannot be used as it might interfere with
> + *   an in-progress slow path operations. In this case the local lock is always
> + *   taken but it still utilizes the freelist for the common operations.

The slub fastpath does not interfere with slow path operations and the
fastpath does not require disabling preemption or interrupts if the
processor supports local rmv operations. So you should be able to use the
fastpath on PREEMPT_RT.

If the fastpath is not possible then you need to disable preemption and
eventually take locks etc and then things may get a bit more complicated.