From: Keith Busch <keith.busch@xxxxxxxxx> Subject: mm/gup: cache dev_pagemap while pinning pages Getting pages from ZONE_DEVICE memory needs to check the backing device's live-ness, which is tracked in the device's dev_pagemap metadata. This metadata is stored in a radix tree and looking it up adds measurable software overhead. This patch avoids repeating this relatively costly operation when dev_pagemap is used by caching the last dev_pagemap while getting user pages. The gup_benchmark kernel self test reports this reduces time to get user pages to as low as 1/3 of the previous time. Link: http://lkml.kernel.org/r/20181012173040.15669-1-keith.busch@xxxxxxxxx Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/huge_mm.h | 8 +- include/linux/mm.h | 12 ---- mm/gup.c | 110 ++++++++++++++++++++++---------------- mm/huge_memory.c | 16 ++--- mm/nommu.c | 6 -- 5 files changed, 79 insertions(+), 73 deletions(-) --- a/include/linux/huge_mm.h~mm-gup-cache-dev_pagemap-while-pinning-pages +++ a/include/linux/huge_mm.h @@ -213,9 +213,9 @@ static inline int hpage_nr_pages(struct } struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, - pmd_t *pmd, int flags); + pmd_t *pmd, int flags, struct dev_pagemap **pgmap); struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, - pud_t *pud, int flags); + pud_t *pud, int flags, struct dev_pagemap **pgmap); extern vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t orig_pmd); @@ -344,13 +344,13 @@ static inline void mm_put_huge_zero_page } static inline struct page *follow_devmap_pmd(struct vm_area_struct *vma, - unsigned long addr, pmd_t *pmd, int flags) + unsigned long addr, pmd_t *pmd, int flags, struct dev_pagemap **pgmap) { return NULL; } static inline struct page *follow_devmap_pud(struct vm_area_struct *vma, - unsigned long addr, pud_t *pud, int flags) + unsigned long addr, pud_t *pud, int flags, struct dev_pagemap **pgmap) { return NULL; } --- a/include/linux/mm.h~mm-gup-cache-dev_pagemap-while-pinning-pages +++ a/include/linux/mm.h @@ -2536,16 +2536,8 @@ static inline vm_fault_t vmf_error(int e return VM_FAULT_SIGBUS; } -struct page *follow_page_mask(struct vm_area_struct *vma, - unsigned long address, unsigned int foll_flags, - unsigned int *page_mask); - -static inline struct page *follow_page(struct vm_area_struct *vma, - unsigned long address, unsigned int foll_flags) -{ - unsigned int unused_page_mask; - return follow_page_mask(vma, address, foll_flags, &unused_page_mask); -} +struct page *follow_page(struct vm_area_struct *vma, unsigned long address, + unsigned int foll_flags); #define FOLL_WRITE 0x01 /* check pte is writable */ #define FOLL_TOUCH 0x02 /* mark page accessed */ --- a/mm/gup.c~mm-gup-cache-dev_pagemap-while-pinning-pages +++ a/mm/gup.c @@ -20,6 +20,11 @@ #include "internal.h" +struct follow_page_context { + struct dev_pagemap *pgmap; + unsigned int page_mask; +}; + static struct page *no_page_table(struct vm_area_struct *vma, unsigned int flags) { @@ -71,10 +76,10 @@ static inline bool can_follow_write_pte( } static struct page *follow_page_pte(struct vm_area_struct *vma, - unsigned long address, pmd_t *pmd, unsigned int flags) + unsigned long address, pmd_t *pmd, unsigned int flags, + struct dev_pagemap **pgmap) { struct mm_struct *mm = vma->vm_mm; - struct dev_pagemap *pgmap = NULL; struct page *page; spinlock_t *ptl; pte_t *ptep, pte; @@ -116,8 +121,8 @@ retry: * Only return device mapping pages in the FOLL_GET case since * they are only valid while holding the pgmap reference. */ - pgmap = get_dev_pagemap(pte_pfn(pte), NULL); - if (pgmap) + *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap); + if (*pgmap) page = pte_page(pte); else goto no_page; @@ -152,15 +157,8 @@ retry: goto retry; } - if (flags & FOLL_GET) { + if (flags & FOLL_GET) get_page(page); - - /* drop the pgmap reference now that we hold the page */ - if (pgmap) { - put_dev_pagemap(pgmap); - pgmap = NULL; - } - } if (flags & FOLL_TOUCH) { if ((flags & FOLL_WRITE) && !pte_dirty(pte) && !PageDirty(page)) @@ -210,7 +208,8 @@ no_page: static struct page *follow_pmd_mask(struct vm_area_struct *vma, unsigned long address, pud_t *pudp, - unsigned int flags, unsigned int *page_mask) + unsigned int flags, + struct follow_page_context *ctx) { pmd_t *pmd, pmdval; spinlock_t *ptl; @@ -258,13 +257,13 @@ retry: } if (pmd_devmap(pmdval)) { ptl = pmd_lock(mm, pmd); - page = follow_devmap_pmd(vma, address, pmd, flags); + page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap); spin_unlock(ptl); if (page) return page; } if (likely(!pmd_trans_huge(pmdval))) - return follow_page_pte(vma, address, pmd, flags); + return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); if ((flags & FOLL_NUMA) && pmd_protnone(pmdval)) return no_page_table(vma, flags); @@ -284,7 +283,7 @@ retry_locked: } if (unlikely(!pmd_trans_huge(*pmd))) { spin_unlock(ptl); - return follow_page_pte(vma, address, pmd, flags); + return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } if (flags & FOLL_SPLIT) { int ret; @@ -307,18 +306,18 @@ retry_locked: } return ret ? ERR_PTR(ret) : - follow_page_pte(vma, address, pmd, flags); + follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } page = follow_trans_huge_pmd(vma, address, pmd, flags); spin_unlock(ptl); - *page_mask = HPAGE_PMD_NR - 1; + ctx->page_mask = HPAGE_PMD_NR - 1; return page; } - static struct page *follow_pud_mask(struct vm_area_struct *vma, unsigned long address, p4d_t *p4dp, - unsigned int flags, unsigned int *page_mask) + unsigned int flags, + struct follow_page_context *ctx) { pud_t *pud; spinlock_t *ptl; @@ -344,7 +343,7 @@ static struct page *follow_pud_mask(stru } if (pud_devmap(*pud)) { ptl = pud_lock(mm, pud); - page = follow_devmap_pud(vma, address, pud, flags); + page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap); spin_unlock(ptl); if (page) return page; @@ -352,13 +351,13 @@ static struct page *follow_pud_mask(stru if (unlikely(pud_bad(*pud))) return no_page_table(vma, flags); - return follow_pmd_mask(vma, address, pud, flags, page_mask); + return follow_pmd_mask(vma, address, pud, flags, ctx); } - static struct page *follow_p4d_mask(struct vm_area_struct *vma, unsigned long address, pgd_t *pgdp, - unsigned int flags, unsigned int *page_mask) + unsigned int flags, + struct follow_page_context *ctx) { p4d_t *p4d; struct page *page; @@ -378,7 +377,7 @@ static struct page *follow_p4d_mask(stru return page; return no_page_table(vma, flags); } - return follow_pud_mask(vma, address, p4d, flags, page_mask); + return follow_pud_mask(vma, address, p4d, flags, ctx); } /** @@ -396,13 +395,13 @@ static struct page *follow_p4d_mask(stru */ struct page *follow_page_mask(struct vm_area_struct *vma, unsigned long address, unsigned int flags, - unsigned int *page_mask) + struct follow_page_context *ctx) { pgd_t *pgd; struct page *page; struct mm_struct *mm = vma->vm_mm; - *page_mask = 0; + ctx->page_mask = 0; /* make this handle hugepd */ page = follow_huge_addr(mm, address, flags & FOLL_WRITE); @@ -431,7 +430,19 @@ struct page *follow_page_mask(struct vm_ return no_page_table(vma, flags); } - return follow_p4d_mask(vma, address, pgd, flags, page_mask); + return follow_p4d_mask(vma, address, pgd, flags, ctx); +} + +struct page *follow_page(struct vm_area_struct *vma, unsigned long address, + unsigned int foll_flags) +{ + struct follow_page_context ctx = { NULL }; + struct page *page; + + page = follow_page_mask(vma, address, foll_flags, &ctx); + if (ctx.pgmap) + put_dev_pagemap(ctx.pgmap); + return page; } static int get_gate_page(struct mm_struct *mm, unsigned long address, @@ -659,9 +670,9 @@ static long __get_user_pages(struct task unsigned int gup_flags, struct page **pages, struct vm_area_struct **vmas, int *nonblocking) { - long i = 0; - unsigned int page_mask; + long ret = 0, i = 0; struct vm_area_struct *vma = NULL; + struct follow_page_context ctx = { NULL }; if (!nr_pages) return 0; @@ -691,12 +702,14 @@ static long __get_user_pages(struct task pages ? &pages[i] : NULL); if (ret) return i ? : ret; - page_mask = 0; + ctx.page_mask = 0; goto next_page; } - if (!vma || check_vma_flags(vma, gup_flags)) - return i ? : -EFAULT; + if (!vma || check_vma_flags(vma, gup_flags)) { + ret = -EFAULT; + goto out; + } if (is_vm_hugetlb_page(vma)) { i = follow_hugetlb_page(mm, vma, pages, vmas, &start, &nr_pages, i, @@ -709,23 +722,26 @@ retry: * If we have a pending SIGKILL, don't keep faulting pages and * potentially allocating memory. */ - if (unlikely(fatal_signal_pending(current))) - return i ? i : -ERESTARTSYS; + if (unlikely(fatal_signal_pending(current))) { + ret = -ERESTARTSYS; + goto out; + } cond_resched(); - page = follow_page_mask(vma, start, foll_flags, &page_mask); + + page = follow_page_mask(vma, start, foll_flags, &ctx); if (!page) { - int ret; ret = faultin_page(tsk, vma, start, &foll_flags, nonblocking); switch (ret) { case 0: goto retry; + case -EBUSY: + ret = 0; + /* FALLTHRU */ case -EFAULT: case -ENOMEM: case -EHWPOISON: - return i ? i : ret; - case -EBUSY: - return i; + goto out; case -ENOENT: goto next_page; } @@ -737,27 +753,31 @@ retry: */ goto next_page; } else if (IS_ERR(page)) { - return i ? i : PTR_ERR(page); + ret = PTR_ERR(page); + goto out; } if (pages) { pages[i] = page; flush_anon_page(vma, page, start); flush_dcache_page(page); - page_mask = 0; + ctx.page_mask = 0; } next_page: if (vmas) { vmas[i] = vma; - page_mask = 0; + ctx.page_mask = 0; } - page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); + page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); if (page_increm > nr_pages) page_increm = nr_pages; i += page_increm; start += page_increm * PAGE_SIZE; nr_pages -= page_increm; } while (nr_pages); - return i; +out: + if (ctx.pgmap) + put_dev_pagemap(ctx.pgmap); + return i ? i : ret; } static bool vma_permits_fault(struct vm_area_struct *vma, --- a/mm/huge_memory.c~mm-gup-cache-dev_pagemap-while-pinning-pages +++ a/mm/huge_memory.c @@ -852,11 +852,10 @@ static void touch_pmd(struct vm_area_str } struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, - pmd_t *pmd, int flags) + pmd_t *pmd, int flags, struct dev_pagemap **pgmap) { unsigned long pfn = pmd_pfn(*pmd); struct mm_struct *mm = vma->vm_mm; - struct dev_pagemap *pgmap; struct page *page; assert_spin_locked(pmd_lockptr(mm, pmd)); @@ -886,12 +885,11 @@ struct page *follow_devmap_pmd(struct vm return ERR_PTR(-EEXIST); pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; - pgmap = get_dev_pagemap(pfn, NULL); - if (!pgmap) + *pgmap = get_dev_pagemap(pfn, *pgmap); + if (!*pgmap) return ERR_PTR(-EFAULT); page = pfn_to_page(pfn); get_page(page); - put_dev_pagemap(pgmap); return page; } @@ -1000,11 +998,10 @@ static void touch_pud(struct vm_area_str } struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, - pud_t *pud, int flags) + pud_t *pud, int flags, struct dev_pagemap **pgmap) { unsigned long pfn = pud_pfn(*pud); struct mm_struct *mm = vma->vm_mm; - struct dev_pagemap *pgmap; struct page *page; assert_spin_locked(pud_lockptr(mm, pud)); @@ -1028,12 +1025,11 @@ struct page *follow_devmap_pud(struct vm return ERR_PTR(-EEXIST); pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; - pgmap = get_dev_pagemap(pfn, NULL); - if (!pgmap) + *pgmap = get_dev_pagemap(pfn, *pgmap); + if (!*pgmap) return ERR_PTR(-EFAULT); page = pfn_to_page(pfn); get_page(page); - put_dev_pagemap(pgmap); return page; } --- a/mm/nommu.c~mm-gup-cache-dev_pagemap-while-pinning-pages +++ a/mm/nommu.c @@ -1709,11 +1709,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, a return ret; } -struct page *follow_page_mask(struct vm_area_struct *vma, - unsigned long address, unsigned int flags, - unsigned int *page_mask) +struct page *follow_page(struct vm_area_struct *vma, unsigned long address, + unsigned int foll_flags) { - *page_mask = 0; return NULL; } _
