Re: [PATCH v2 0/2] mm: Remember a/d bits for migration entries

Nadav Amit
2022-08-04T22:17:51Z

On Aug 4, 2022, at 1:39 PM, Peter Xu <peterx@redhat.com> wrote:

> (1) Page Idle Tracking
>
> Before this series, idle tracking can cause false negative if an accessed
> page got migrated, since after migration the young bit will get lost.
> After this series, it'll be better in that after migration young bit will
> be persisted, so it'll be able to be detected correctly by page idle
> logic when walking the pgtable.
>
> However there's still nothing done when page idle reset was carried out
> during migration procedure in progress, but that should be a separate
> topic to be addressed (e.g. to teach rmap pgtable walk code to be able to
> walk with both present ptes and migration ptes).

IIUC, when a migration entry is set page_remove_rmap() is called by
try_to_migrate_one(), so improving page-idle accuracy should be done in a
different way.