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Date: Thu, 16 Jun 2022 11:48:56 +0800 From: Baolin Wang <baolin.wang@...ux.alibaba.com> To: Mike Kravetz <mike.kravetz@...cle.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, Muchun Song <songmuchun@...edance.com>, Michal Hocko <mhocko@...e.com>, Peter Xu <peterx@...hat.com>, Naoya Horiguchi <naoya.horiguchi@...ux.dev>, James Houghton <jthoughton@...gle.com>, Mina Almasry <almasrymina@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>, Anshuman Khandual <anshuman.khandual@....com>, Paul Walmsley <paul.walmsley@...ive.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [RFC PATCH 1/3] hugetlb: skip to end of PT page mapping when pte not present On 6/16/2022 5:22 AM, Mike Kravetz wrote: > On 05/30/22 18:10, Baolin Wang wrote: >> >> >> On 5/28/2022 6:58 AM, Mike Kravetz wrote: >>> HugeTLB address ranges are linearly scanned during fork, unmap and >>> remap operations. If a non-present entry is encountered, the code >>> currently continues to the next huge page aligned address. However, >>> a non-present entry implies that the page table page for that entry >>> is not present. Therefore, the linear scan can skip to the end of >>> range mapped by the page table page. This can speed operations on >>> large sparsely populated hugetlb mappings. >>> >>> Create a new routine hugetlb_mask_last_hp() that will return an >>> address mask. When the mask is ORed with an address, the result >>> will be the address of the last huge page mapped by the associated >>> page table page. Use this mask to update addresses in routines which >>> linearly scan hugetlb address ranges when a non-present pte is >>> encountered. >>> >>> hugetlb_mask_last_hp is related to the implementation of huge_pte_offset >>> as hugetlb_mask_last_hp is called when huge_pte_offset returns NULL. >>> This patch only provides a complete hugetlb_mask_last_hp implementation >>> when CONFIG_ARCH_WANT_GENERAL_HUGETLB is defined. Architectures which >>> provide their own versions of huge_pte_offset can also provide their own >>> version of hugetlb_mask_last_hp. >> >> I tested on my ARM64 machine with implementing arm64 specific >> hugetlb_mask_last_hp() as below, and it works well. >> >> Just a few nits inline, otherwise looks good to me. >> Tested-by: Baolin Wang <baolin.wang@...ux.alibaba.com> >> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com> >> >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index d93ba128a2b0..e04a097ffcc4 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -376,6 +376,28 @@ pte_t *huge_pte_offset(struct mm_struct *mm, >> return NULL; >> } >> >> +unsigned long hugetlb_mask_last_hp(struct hstate *h) >> +{ >> + unsigned long hp_size = huge_page_size(h); >> + >> + switch (hp_size) { >> + case P4D_SIZE: >> + return PGDIR_SIZE - P4D_SIZE; >> + case PUD_SIZE: >> + return P4D_SIZE - PUD_SIZE; >> + case CONT_PMD_SIZE: >> + return PUD_SIZE - CONT_PMD_SIZE; >> + case PMD_SIZE: >> + return PUD_SIZE - PMD_SIZE; >> + case CONT_PTE_SIZE: >> + return PMD_SIZE - CONT_PTE_SIZE; >> + default: >> + break; >> + } >> + >> + return ~(0UL); >> +} > > Hello Baolin, > > Would you mind sending this as a proper patch with commit message and > 'Signed-off-by:'? I would like to include it in the upcoming patch series. Sure. I've sent it out [1], and please fold it into your series. Thanks. [1] https://lore.kernel.org/all/7256dbe078d7231f45b0f47c2c52a3bd3aa10da7.1655350193.git.baolin.wang@linux.alibaba.com/
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