Messages in this thread | | | Subject | Re: [PATCH v4 4/8] mm/rmap: Split migration into its own function | From | Ralph Campbell <> | Date | Mon, 8 Mar 2021 10:58:12 -0800 |
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On 3/3/21 10:16 PM, Alistair Popple wrote: > Migration is currently implemented as a mode of operation for > try_to_unmap_one() generally specified by passing the TTU_MIGRATION flag > or in the case of splitting a huge anonymous page TTU_SPLIT_FREEZE. > > However it does not have much in common with the rest of the unmap > functionality of try_to_unmap_one() and thus splitting it into a > separate function reduces the complexity of try_to_unmap_one() making it > more readable. > > Several simplifications can also be made in try_to_migrate_one() based > on the following observations: > > - All users of TTU_MIGRATION also set TTU_IGNORE_MLOCK. > - No users of TTU_MIGRATION ever set TTU_IGNORE_HWPOISON. > - No users of TTU_MIGRATION ever set TTU_BATCH_FLUSH. > > TTU_SPLIT_FREEZE is a special case of migration used when splitting an > anonymous page. This is most easily dealt with by calling the correct > function from unmap_page() in mm/huge_memory.c - either > try_to_migrate() for PageAnon or try_to_unmap(). > > Signed-off-by: Alistair Popple <apopple@nvidia.com> > Reviewed-by: Christoph Hellwig <hch@lst.de>
Looks reasonable to me. I do worry a bit about code duplication. At some point in the future, it might be discovered that other combinations of TTU_XXX flags are needed in which case a careful check of try_to_migrate() and try_to_unmap() will be needed.
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
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