Messages in this thread |  | | Date | Sun, 22 Nov 2020 19:00:02 +0000 | From | Matthew Wilcox <> | Subject | Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two |
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On Fri, Nov 20, 2020 at 09:25:52AM +0100, Michal Hocko wrote: > On Fri 20-11-20 14:43:25, Muchun Song wrote: > > We only can free the unused vmemmap to the buddy system when the > > size of struct page is a power of two. > > Can we actually have !power_of_2 struct pages?
Yes. On x86-64, if you don't enable MEMCG, it's 56 bytes. On SPARC64, if you do enable MEMCG, it's 72 bytes. On 32-bit systems, it's anything from 32-44 bytes, depending on MEMCG, WANT_PAGE_VIRTUAL and LAST_CPUPID_NOT_IN_PAGE_FLAGS.
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