Re: [PATCH v4 01/16] mm: thp: Batch-collapse PMD with set_ptes()

[Ryan Roberts]

On 18/12/2023 17:40, David Hildenbrand wrote:
> On 18.12.23 11:50, Ryan Roberts wrote:
>> Refactor __split_huge_pmd_locked() so that a present PMD can be
>> collapsed to PTEs in a single batch using set_ptes(). It also provides a
>> future opportunity to batch-add the folio to the rmap using David's new
>> batched rmap APIs.
> 
> I'd drop that sentence and rather just say "In the future, we might get rid of
> the remaining manual loop by using rmap batching.".

OK fair enough. Will fix for next version.

> 
>>
>> This should improve performance a little bit, but the real motivation is
>> to remove the need for the arm64 backend to have to fold the contpte
>> entries. Instead, since the ptes are set as a batch, the contpte blocks
>> can be initially set up pre-folded (once the arm64 contpte support is
>> added in the next few patches). This leads to noticeable performance
>> improvement during split.
>>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>

Thanks!