On 30/06/2024 00:41, Barry Song wrote:
> From: Barry Song <v-songbaohua@xxxxxxxx>
>
> The optimization of list_empty(&folio->_deferred_list) aimed to prevent
> increasing the PTL duration when a large folio is partially unmapped,
> for example, from subpage 0 to subpage (nr - 2).
>
> But Ryan's commit 5ed890ce5147 ("mm: vmscan: avoid split during
> shrink_folio_list()") actually splits this kind of large folios. This
> makes the "optimization" useless.
>
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> ---
> -v1
> * I remember David and Ryan once suggested that this check could be dropped
> while the patch was being pulled into mm-unstable. However, for some reason,
> I forgot to request squashing this change.
>
> mm/vmscan.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3d4c681c6d40..0761f91b407f 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1291,7 +1291,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
> * try_to_unmap acquire PTL from the first PTE,
> * eliminating the influence of temporary PTE values.
> */
> - if (folio_test_large(folio) && list_empty(&folio->_deferred_list))
> + if (folio_test_large(folio))
As it stands, the list_empty() technically needs a data_race() annotation. I
think your original patch went into v6.10-rc1? If so, perhaps it makes sense to
try to get this into the next rc?
> flags |= TTU_SYNC;
>
> try_to_unmap(folio, flags);
