| Date | Sun, 29 Mar 2015 20:51:38 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv4 15/24] mm, thp: remove infrastructure for handling splitting PMDs |
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On Sun, Mar 29, 2015 at 09:40:07PM +0530, Aneesh Kumar K.V wrote: > "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes: > > > With new refcounting we don't need to mark PMDs splitting. Let's drop code > > to handle this. > > > > Arch-specific code will removed separately. > > > > Can you explain this more ? Why we don't care of PMD splitting case even > w.r.t to split_huge_page() ?
It used to be required to keep kernel from updating page refcounts while we splitting the page. Now with split_huge_pmd() we can split one PMD a time without blocking refcounting. Once all PMDs split we can freeze the page's refcounts with compound lock[1] and split underlying compound page.
[1] compound lock is replaced with migration entries by the end of the patchset.
-- Kirill A. Shutemov
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