Re: [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.