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| author | Keith Busch <keith.busch@intel.com> | 2018-10-26 15:10:28 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-10-26 16:38:15 -0700 |
| commit | df06b37ffe5a442503b7095b77b0a970df515459 (patch) | |
| tree | 2fdb301eba4b4c2240595040496096b3a6489c79 /mm/huge_memory.c | |
| parent | 9fd61bc95130d4971568b89c9548b5e0a4e18e0e (diff) | |
| download | lwn-df06b37ffe5a442503b7095b77b0a970df515459.tar.gz lwn-df06b37ffe5a442503b7095b77b0a970df515459.zip | |
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@intel.com
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 16 |
1 files changed, 6 insertions, 10 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8ea1b36bd452..25c7d7509cf4 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -852,11 +852,10 @@ static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, } 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_area_struct *vma, unsigned long addr, 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_struct *vma, unsigned long addr, } 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_area_struct *vma, unsigned long addr, 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; } |