Re: [PATCH RFC v2] mm: introduce copy_mc_highpages() and batch copy in folio_mc_copy()

[David Hildenbrand (Arm)]

On 10/19/26 15:10, Garg, Shivank wrote:
> On Mon, 2026-10-19 at 14:23 +0200, David Hildenbrand (Arm) wrote:
>>>
>>> I would suggest that perhaps this should be the fallback for non-preemptible
>>> models. But it gets a little weird with PREEMPT_DYNAMIC I think?
>>
>> Why can't we just use PROCESS_PAGES_NON_PREEMPT_BATCH where we have similar
>> handling already?
>>
>>>
> 
> I did not reuse PROCESS_PAGES_NON_PREEMPT_BATCH because it depends on
> whether clear_pages is defined. While COPY_MC_PAGES_NON_PREEMPT_BATCH
> depends on copy_mc_to_kernel and other constraints. So, using a single
> param for both would make it more messy.

If it would stay it would all have to be cleaned up to end up with a single one.

> 
> However as Pedro pointed, most architectures are full preempt/preempt lazy,
> and with this commit 7dadeaa6e851 ("sched: Further restrict the
> preemption modes"), for PREEMPT_DYNAMIC, preempt=none and preempt=voluntary
> are rejected at boot. preempt_model_preemptible() is therefore always
> true for this case.
> 
> So, this can be simplfied to drop the COPY_MC_PAGES_NON_PREEMPT_BATCH.

Can we simplify the zeroing part as well?

-- 
Cheers,

David