From: Ryan Roberts ryan.roberts@arm.com
mainline inclusion from mainline-v6.8-rc1 commit 19eaf44954df64f9bc8dec398219e15ad0811497 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I98AW9 CVE: NA
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Introduce the logic to allow THP to be configured (through the new sysfs interface we just added) to allocate large folios to back anonymous memory, which are larger than the base page size but smaller than PMD-size. We call this new THP extension "multi-size THP" (mTHP).
mTHP continues to be PTE-mapped, but in many cases can still provide similar benefits to traditional PMD-sized THP: Page faults are significantly reduced (by a factor of e.g. 4, 8, 16, etc. depending on the configured order), but latency spikes are much less prominent because the size of each page isn't as huge as the PMD-sized variant and there is less memory to clear in each page fault. The number of per-page operations (e.g. ref counting, rmap management, lru list management) are also significantly reduced since those ops now become per-folio.
Some architectures also employ TLB compression mechanisms to squeeze more entries in when a set of PTEs are virtually and physically contiguous and approporiately aligned. In this case, TLB misses will occur less often.
The new behaviour is disabled by default, but can be enabled at runtime by writing to /sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled (see documentation in previous commit). The long term aim is to change the default to include suitable lower orders, but there are some risks around internal fragmentation that need to be better understood first.
[ryan.roberts@arm.com: resolve some multi-size THP review nits] Link: https://lkml.kernel.org/r/20231214160251.3574571-1-ryan.roberts@arm.com Link: https://lkml.kernel.org/r/20231207161211.2374093-5-ryan.roberts@arm.com Signed-off-by: Ryan Roberts ryan.roberts@arm.com Tested-by: Kefeng Wang wangkefeng.wang@huawei.com Tested-by: John Hubbard jhubbard@nvidia.com Acked-by: David Hildenbrand david@redhat.com Cc: Alistair Popple apopple@nvidia.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Barry Song v-songbaohua@oppo.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: David Rientjes rientjes@google.com Cc: "Huang, Ying" ying.huang@intel.com Cc: Hugh Dickins hughd@google.com Cc: Itaru Kitayama itaru.kitayama@gmail.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Luis Chamberlain mcgrof@kernel.org Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Yang Shi shy828301@gmail.com Cc: Yin Fengwei fengwei.yin@intel.com Cc: Yu Zhao yuzhao@google.com Cc: Zi Yan ziy@nvidia.com Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 19eaf44954df64f9bc8dec398219e15ad0811497) Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com --- include/linux/huge_mm.h | 6 ++- mm/memory.c | 111 ++++++++++++++++++++++++++++++++++++---- 2 files changed, 105 insertions(+), 12 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 609c153bae57..fa7a38a30fc6 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -68,9 +68,11 @@ extern struct kobj_attribute shmem_enabled_attr; #define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
/* - * Mask of all large folio orders supported for anonymous THP. + * Mask of all large folio orders supported for anonymous THP; all orders up to + * and including PMD_ORDER, except order-0 (which is not "huge") and order-1 + * (which is a limitation of the THP implementation). */ -#define THP_ORDERS_ALL_ANON BIT(PMD_ORDER) +#define THP_ORDERS_ALL_ANON ((BIT(PMD_ORDER + 1) - 1) & ~(BIT(0) | BIT(1)))
/* * Mask of all large folio orders supported for file THP. diff --git a/mm/memory.c b/mm/memory.c index 2b1fde55ee66..9a0b8f2f6f4b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4117,6 +4117,84 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) return ret; }
+static bool pte_range_none(pte_t *pte, int nr_pages) +{ + int i; + + for (i = 0; i < nr_pages; i++) { + if (!pte_none(ptep_get_lockless(pte + i))) + return false; + } + + return true; +} + +static struct folio *alloc_anon_folio(struct vm_fault *vmf) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + struct vm_area_struct *vma = vmf->vma; + unsigned long orders; + struct folio *folio; + unsigned long addr; + pte_t *pte; + gfp_t gfp; + int order; + + /* + * If uffd is active for the vma we need per-page fault fidelity to + * maintain the uffd semantics. + */ + if (unlikely(userfaultfd_armed(vma))) + goto fallback; + + /* + * Get a list of all the (large) orders below PMD_ORDER that are enabled + * for this vma. Then filter out the orders that can't be allocated over + * the faulting address and still be fully contained in the vma. + */ + orders = thp_vma_allowable_orders(vma, vma->vm_flags, false, true, true, + BIT(PMD_ORDER) - 1); + orders = thp_vma_suitable_orders(vma, vmf->address, orders); + + if (!orders) + goto fallback; + + pte = pte_offset_map(vmf->pmd, vmf->address & PMD_MASK); + if (!pte) + return ERR_PTR(-EAGAIN); + + /* + * Find the highest order where the aligned range is completely + * pte_none(). Note that all remaining orders will be completely + * pte_none(). + */ + order = highest_order(orders); + while (orders) { + addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); + if (pte_range_none(pte + pte_index(addr), 1 << order)) + break; + order = next_order(&orders, order); + } + + pte_unmap(pte); + + /* Try allocating the highest of the remaining orders. */ + gfp = vma_thp_gfp_mask(vma); + while (orders) { + addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); + folio = vma_alloc_folio(gfp, order, vma, addr, true); + if (folio) { + clear_huge_page(&folio->page, vmf->address, 1 << order); + return folio; + } + order = next_order(&orders, order); + } + +fallback: +#endif + return vma_alloc_zeroed_movable_folio(vmf->vma, vmf->address); +} + /* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -4126,9 +4204,12 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) { bool uffd_wp = vmf_orig_pte_uffd_wp(vmf); struct vm_area_struct *vma = vmf->vma; + unsigned long addr = vmf->address; struct folio *folio; vm_fault_t ret = 0; + int nr_pages = 1; pte_t entry; + int i;
/* File mapping without ->vm_ops ? */ if (vma->vm_flags & VM_SHARED) @@ -4168,10 +4249,16 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) /* Allocate our own private page. */ if (unlikely(anon_vma_prepare(vma))) goto oom; - folio = vma_alloc_zeroed_movable_folio(vma, vmf->address); + /* Returns NULL on OOM or ERR_PTR(-EAGAIN) if we must retry the fault */ + folio = alloc_anon_folio(vmf); + if (IS_ERR(folio)) + return 0; if (!folio) goto oom;
+ nr_pages = folio_nr_pages(folio); + addr = ALIGN_DOWN(vmf->address, nr_pages * PAGE_SIZE); + if (mem_cgroup_charge(folio, vma->vm_mm, GFP_KERNEL)) goto oom_free_page; folio_throttle_swaprate(folio, GFP_KERNEL); @@ -4188,12 +4275,15 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry), vma);
- vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, - &vmf->ptl); + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl); if (!vmf->pte) goto release; - if (vmf_pte_changed(vmf)) { - update_mmu_tlb(vma, vmf->address, vmf->pte); + if (nr_pages == 1 && vmf_pte_changed(vmf)) { + update_mmu_tlb(vma, addr, vmf->pte); + goto release; + } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) { + for (i = 0; i < nr_pages; i++) + update_mmu_tlb(vma, addr + PAGE_SIZE * i, vmf->pte + i); goto release; }
@@ -4208,17 +4298,18 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) return handle_userfault(vmf, VM_UFFD_MISSING); }
- inc_mm_counter(vma->vm_mm, MM_ANONPAGES); - add_reliable_folio_counter(folio, vma->vm_mm, 1); - folio_add_new_anon_rmap(folio, vma, vmf->address); + folio_ref_add(folio, nr_pages - 1); + add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages); + add_reliable_folio_counter(folio, vma->vm_mm, nr_pages); + folio_add_new_anon_rmap(folio, vma, addr); folio_add_lru_vma(folio, vma); setpte: if (uffd_wp) entry = pte_mkuffd_wp(entry); - set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry); + set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr_pages);
/* No need to invalidate - it was non-present before */ - update_mmu_cache_range(vmf, vma, vmf->address, vmf->pte, 1); + update_mmu_cache_range(vmf, vma, addr, vmf->pte, nr_pages); unlock: if (vmf->pte) pte_unmap_unlock(vmf->pte, vmf->ptl);