Messages in this thread | | | Date | Mon, 23 Jan 2023 12:09:22 +0100 | Subject | Re: [PATCH] mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma | From | David Hildenbrand <> |
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On 18.01.23 00:00, Zach O'Keefe wrote: > On Mon, Jan 9, 2023 at 12:50 AM David Hildenbrand <david@redhat.com> wrote: >> >>>>>>>> >>>>>>>> Side note: set_huge_pmd() wins the award of "ugliest mm function of early >>>>>>>> 2023". I was briefly concerned how do_set_pmd() decides whether the PMD can be >>>>>>>> writable or not. Turns out it's communicated via vm_fault->flags. Just >>>>>>>> horrible. >>> > > Hey David, > > Sorry for the late response here. > >>> My first Linux award! :) At least it's not "worst mm security issue of >>> early 2023". I'll take it! >> >> Good that you're not taking my words the wrong way. >> >> MADV_COLLAPSE is a very useful feature (especially also for THP tests >> [1]). I wish I could have looked at some of the patches earlier. But we >> cannot wait forever to get something merged, otherwise we'd never get >> bigger changes upstream. >> >> ... so there is plenty of time left in 2023 to cleanup khugepaged.c :P >> >> >> [1] https://lkml.kernel.org/r/20230104144905.460075-1-david@redhat.com > > Yes, thank you for these tests. I have them open in another tab along > with a mental TODO to take a closer look at them, and response > half-written. In-place collapse of anonymous memory *is* something > that I was interested in exploring later (I have a use-case for it; > hugepage-aware malloc() implementations). I'm taking so long on it > (sorry) b/c I need to review your point (2) (all PTE's mapping > exclusively). Hopefully I can get to it shortly.
Cool, please let me know if you have any questions. Being able to in-place collapse a PTE-mapped anon THP again would be nice.
-- Thanks,
David / dhildenb
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