Messages in this thread | | | Date | Mon, 26 Feb 2024 09:41:33 +0100 | Subject | Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise_free | From | David Hildenbrand <> |
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On 26.02.24 09:37, Lance Yang wrote: > Hey Barry, > > Thanks for taking time to review! > > On Mon, Feb 26, 2024 at 12:00 PM Barry Song <21cnbao@gmail.com> wrote: > [...] >> On Mon, Feb 26, 2024 at 1:33 AM Lance Yang <ioworker0@gmail.com> wrote: > [...] >> We did something similar on MADV_PAGEOUT[1] >> [1] https://lore.kernel.org/linux-mm/20240118111036.72641-7-21cnbao@gmail.com/ > > Thanks for providing the link above. > > [...] >>> + * Avoid unnecessary folio splitting if the large >>> + * folio is entirely within the given range. >>> + */ >>> + folio_test_clear_dirty(folio); >>> + folio_unlock(folio); >>> + for (; addr != next_addr; pte++, addr += PAGE_SIZE) { >>> + ptent = ptep_get(pte); >>> + if (pte_young(ptent) || pte_dirty(ptent)) { >>> + ptent = ptep_get_and_clear_full( >>> + mm, addr, pte, tlb->fullmm); >>> + ptent = pte_mkold(ptent); >>> + ptent = pte_mkclean(ptent); >>> + set_pte_at(mm, addr, pte, ptent); >>> + tlb_remove_tlb_entry(tlb, pte, addr); >>> + } >> >> The code works under the assumption the large folio is entirely mapped >> in all PTEs in the range. This is not always true. >> >> This won't work in some cases as some PTEs might be mapping to the >> large folios. some others might have been unmapped or mapped >> to different folios. >> >> so in MADV_PAGEOUT, we have a function to check the folio is >> really entirely mapped: >> >> +static inline bool pte_range_cont_mapped(unsigned long start_pfn, >> + pte_t *start_pte, unsigned long start_addr, int nr) >> +{ >> + int i; >> + pte_t pte_val; >> + >> + for (i = 0; i < nr; i++) { >> + pte_val = ptep_get(start_pte + i); >> + >> + if (pte_none(pte_val)) >> + return false; >> + >> + if (pte_pfn(pte_val) != (start_pfn + i)) >> + return false; >> + } >> + >> + return true; >> +} > > Thanks for providing the information; it's very helpful to me! > I made some changes. Would you mind taking another look, please? > > As a diff against this patch. > > diff --git a/mm/madvise.c b/mm/madvise.c > index bcbf56595a2e..255d2f329be4 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -616,6 +616,18 @@ static long madvise_pageout(struct vm_area_struct *vma, > return 0; > } > > +static inline bool pte_range_cont_mapped(pte_t *pte, unsigned long nr) > +{ > + pte_t pte_val; > + unsigned long pfn = pte_pfn(pte); > + for (int i = 0; i < nr; i++) { > + pte_val = ptep_get(pte + i); > + if (pte_none(pte_val) || pte_pfn(pte_val) != (pfn + i)) > + return false; > + } > + return true; > +}
I dislike the "cont mapped" terminology.
Maybe folio_pte_batch() does what you want?
-- Cheers,
David / dhildenb
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