| Date | Tue, 09 Jun 2015 15:59:40 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCHv6 13/36] mm: drop tail page refcounting |
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On 06/03/2015 07:05 PM, Kirill A. Shutemov wrote: > Tail page refcounting is utterly complicated and painful to support. > > It uses ->_mapcount on tail pages to store how many times this page is > pinned. get_page() bumps ->_mapcount on tail page in addition to > ->_count on head. This information is required by split_huge_page() to > be able to distribute pins from head of compound page to tails during > the split. > > We will need ->_mapcount acoount PTE mappings of subpages of the
to account
> compound page. We eliminate need in current meaning of ->_mapcount in > tail pages by forbidding split entirely if the page is pinned. > > The only user of tail page refcounting is THP which is marked BROKEN for > now. > > Let's drop all this mess. It makes get_page() and put_page() much > simpler. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Tested-by: Sasha Levin <sasha.levin@oracle.com> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
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