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Mon, 06 Mar 2023 15:00:11 -0800 (PST) Date: Mon, 6 Mar 2023 23:00:03 +0000 In-Reply-To: <20230306230004.1387007-1-jthoughton@google.com> Mime-Version: 1.0 References: <20230306230004.1387007-1-jthoughton@google.com> X-Mailer: git-send-email 2.40.0.rc0.216.gc4246ad0f0-goog Message-ID: <20230306230004.1387007-2-jthoughton@google.com> Subject: [PATCH 1/2] mm: rmap: make hugetlb pages participate in _nr_pages_mapped From: James Houghton To: Mike Kravetz , Hugh Dickins , Muchun Song , Peter Xu , "Matthew Wilcox (Oracle)" , Andrew Morton Cc: "Kirill A . Shutemov" , David Hildenbrand , David Rientjes , Axel Rasmussen , Jiaqi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, James Houghton X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: mciw8druk3bgmksareutqjky3p4ou365 X-Rspamd-Queue-Id: B8EEF1C0026 X-HE-Tag: 1678143612-95888 X-HE-Meta: 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 iUjmCpMU 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: For compound mappings (compound=true), _nr_pages_mapped will now be incremented by COMPOUND_MAPPED when the first compound mapping is created. For small mappings, _nr_pages_mapped is incremented by 1 when the particular small page is mapped for the first time. This is incompatible with HPageVmemmapOptimize()ed folios, as most of the tail page structs will be mapped read-only. Currently HugeTLB always passes compound=true, but in the future, HugeTLB pages may be mapped with small mappings. To implement this change: 1. Replace most of HugeTLB's calls to page_dup_file_rmap() with page_add_file_rmap(). The call in copy_hugetlb_page_range() is kept. 2. Update page_add_file_rmap() and page_remove_rmap() to support HugeTLB folios. 3. Update hugepage_add_anon_rmap() and hugepage_add_new_anon_rmap() to also increment _nr_pages_mapped properly. With these changes, folio_large_is_mapped() no longer needs to check _entire_mapcount. HugeTLB doesn't use LRU or mlock, so page_add_file_rmap() and page_remove_rmap() excludes those pieces. It is also important that the folio_test_pmd_mappable() check is removed (or changed), as it's possible to have a HugeTLB page whose order is not >= HPAGE_PMD_ORDER, like arm64's CONT_PTE_SIZE HugeTLB pages. This patch limits HugeTLB pages to 16G in size. That limit can be increased if COMPOUND_MAPPED is raised. Signed-off-by: James Houghton Acked-by: Mike Kravetz diff --git a/include/linux/mm.h b/include/linux/mm.h index ce1590933995..25c898c51129 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1143,12 +1143,7 @@ static inline int total_mapcount(struct page *page) static inline bool folio_large_is_mapped(struct folio *folio) { - /* - * Reading _entire_mapcount below could be omitted if hugetlb - * participated in incrementing nr_pages_mapped when compound mapped. - */ - return atomic_read(&folio->_nr_pages_mapped) > 0 || - atomic_read(&folio->_entire_mapcount) >= 0; + return atomic_read(&folio->_nr_pages_mapped) > 0; } /** diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 07abcb6eb203..bf3d327cd1b9 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5911,7 +5911,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, if (anon_rmap) hugepage_add_new_anon_rmap(folio, vma, haddr); else - page_dup_file_rmap(&folio->page, true); + page_add_file_rmap(&folio->page, vma, true); new_pte = make_huge_pte(vma, &folio->page, ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))); /* @@ -6293,7 +6293,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, goto out_release_unlock; if (folio_in_pagecache) - page_dup_file_rmap(&folio->page, true); + page_add_file_rmap(&folio->page, dst_vma, true); else hugepage_add_new_anon_rmap(folio, dst_vma, dst_addr); diff --git a/mm/internal.h b/mm/internal.h index fce94775819c..400451a4dd49 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -55,8 +55,7 @@ void page_writeback_init(void); /* * If a 16GB hugetlb folio were mapped by PTEs of all of its 4kB pages, * its nr_pages_mapped would be 0x400000: choose the COMPOUND_MAPPED bit - * above that range, instead of 2*(PMD_SIZE/PAGE_SIZE). Hugetlb currently - * leaves nr_pages_mapped at 0, but avoid surprise if it participates later. + * above that range, instead of 2*(PMD_SIZE/PAGE_SIZE). */ #define COMPOUND_MAPPED 0x800000 #define FOLIO_PAGES_MAPPED (COMPOUND_MAPPED - 1) diff --git a/mm/migrate.c b/mm/migrate.c index 476cd24e8f32..c95c1cbc7a47 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -254,7 +254,7 @@ static bool remove_migration_pte(struct folio *folio, hugepage_add_anon_rmap(new, vma, pvmw.address, rmap_flags); else - page_dup_file_rmap(new, true); + page_add_file_rmap(new, vma, true); set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); } else #endif diff --git a/mm/rmap.c b/mm/rmap.c index ba901c416785..4a975429b91a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1316,19 +1316,21 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, int nr = 0, nr_pmdmapped = 0; bool first; - VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); + VM_BUG_ON_PAGE(compound && !PageTransHuge(page) + && !folio_test_hugetlb(folio), page); /* Is page being mapped by PTE? Is this its first map to be added? */ if (likely(!compound)) { + if (unlikely(folio_test_hugetlb(folio))) + VM_BUG_ON_PAGE(HPageVmemmapOptimized(&folio->page), + page); first = atomic_inc_and_test(&page->_mapcount); nr = first; if (first && folio_test_large(folio)) { nr = atomic_inc_return_relaxed(mapped); nr = (nr < COMPOUND_MAPPED); } - } else if (folio_test_pmd_mappable(folio)) { - /* That test is redundant: it's for safety or to optimize out */ - + } else { first = atomic_inc_and_test(&folio->_entire_mapcount); if (first) { nr = atomic_add_return_relaxed(COMPOUND_MAPPED, mapped); @@ -1345,6 +1347,9 @@ void page_add_file_rmap(struct page *page, struct vm_area_struct *vma, } } + if (folio_test_hugetlb(folio)) + return; + if (nr_pmdmapped) __lruvec_stat_mod_folio(folio, folio_test_swapbacked(folio) ? NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped); @@ -1373,24 +1378,18 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma, VM_BUG_ON_PAGE(compound && !PageHead(page), page); - /* Hugetlb pages are not counted in NR_*MAPPED */ - if (unlikely(folio_test_hugetlb(folio))) { - /* hugetlb pages are always mapped with pmds */ - atomic_dec(&folio->_entire_mapcount); - return; - } - /* Is page being unmapped by PTE? Is this its last map to be removed? */ if (likely(!compound)) { + if (unlikely(folio_test_hugetlb(folio))) + VM_BUG_ON_PAGE(HPageVmemmapOptimized(&folio->page), + page); last = atomic_add_negative(-1, &page->_mapcount); nr = last; if (last && folio_test_large(folio)) { nr = atomic_dec_return_relaxed(mapped); nr = (nr < COMPOUND_MAPPED); } - } else if (folio_test_pmd_mappable(folio)) { - /* That test is redundant: it's for safety or to optimize out */ - + } else { last = atomic_add_negative(-1, &folio->_entire_mapcount); if (last) { nr = atomic_sub_return_relaxed(COMPOUND_MAPPED, mapped); @@ -1407,6 +1406,9 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma, } } + if (folio_test_hugetlb(folio)) + return; + if (nr_pmdmapped) { if (folio_test_anon(folio)) idx = NR_ANON_THPS; @@ -2541,9 +2543,11 @@ void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma, first = atomic_inc_and_test(&folio->_entire_mapcount); VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page); - if (first) + if (first) { + atomic_add(COMPOUND_MAPPED, &folio->_nr_pages_mapped); __page_set_anon_rmap(folio, page, vma, address, !!(flags & RMAP_EXCLUSIVE)); + } } void hugepage_add_new_anon_rmap(struct folio *folio, @@ -2552,6 +2556,7 @@ void hugepage_add_new_anon_rmap(struct folio *folio, BUG_ON(address < vma->vm_start || address >= vma->vm_end); /* increment count (starts at -1) */ atomic_set(&folio->_entire_mapcount, 0); + atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED); folio_clear_hugetlb_restore_reserve(folio); __page_set_anon_rmap(folio, &folio->page, vma, address, 1); }