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Date: Mon, 27 Jun 2022 09:48:28 -0700 From: James Houghton <jthoughton@...gle.com> To: Matthew Wilcox <willy@...radead.org> Cc: Mike Kravetz <mike.kravetz@...cle.com>, Muchun Song <songmuchun@...edance.com>, Peter Xu <peterx@...hat.com>, David Hildenbrand <david@...hat.com>, David Rientjes <rientjes@...gle.com>, Axel Rasmussen <axelrasmussen@...gle.com>, Mina Almasry <almasrymina@...gle.com>, Jue Wang <juew@...gle.com>, Manish Mishra <manish.mishra@...anix.com>, "Dr . David Alan Gilbert" <dgilbert@...hat.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH 00/26] hugetlb: Introduce HugeTLB high-granularity mapping On Fri, Jun 24, 2022 at 11:47 AM Matthew Wilcox <willy@...radead.org> wrote: > > On Fri, Jun 24, 2022 at 05:36:30PM +0000, James Houghton wrote: > > - Page table walking and manipulation > > A new function, hugetlb_walk_to, handles walking HugeTLB page tables for > > high-granularity mappings. Eventually, it's possible to merge > > hugetlb_walk_to with huge_pte_offset and huge_pte_alloc. > > > > We keep track of HugeTLB page table entries with a new struct, hugetlb_pte. > > This is because we generally need to know the "size" of a PTE (previously > > always just huge_page_size(hstate)). > > > > For every page table manipulation function that has a huge version (e.g. > > huge_ptep_get and ptep_get), there is a wrapper for it (e.g. > > hugetlb_ptep_get). The correct version is used depending on if a HugeTLB > > PTE really is "huge". > > I'm disappointed to hear that page table walking is going to become even > more special. I'd much prefer it if hugetlb walking were exactly the > same as THP walking. This seems like a good time to do at least some > of that work. > > Was there a reason you chose the "more complexity" direction? I chose this direction because it seemed to be the most straightforward to get to a working prototype and then to an RFC. I agree with your sentiment -- I'll see what I can do to reconcile THP walking with HugeTLB(+HGM) walking.
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