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SubjectRe: [PATCH v4 05/10] mm/gup: migrate pinned pages out of movable zone
On Thu 17-12-20 13:52:38, Pavel Tatashin wrote:
> + * 1. Pinned pages: (long-term) pinning of movable pages is avoided
> + * when pages are pinned and faulted, but it is still possible that
> + * address space already has pages in ZONE_MOVABLE at the time when
> + * pages are pinned (i.e. user has touches that memory before
> + * pinning). In such case we try to migrate them to a different zone,
> + * but if migration fails the pages can still end-up pinned in
> + * ZONE_MOVABLE. In such case, memory offlining might retry a long
> + * time and will only succeed once user application unpins pages.

I still dislike this. Pinning can fail so there shouldn't be any reasons
to break MOVABLE constrain for something that can be handled. If
anything there should be a very good reasoning behind this decision
documented.
--
Michal Hocko
SUSE Labs

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