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mm/gup: cache dev_pagemap while pinning pages

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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>
This commit is contained in:
Keith Busch
2018-10-26 15:10:28 -07:00
committed by Linus Torvalds
parent 9fd61bc951
commit df06b37ffe
5 changed files with 79 additions and 73 deletions
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8
include/linux/huge_mm.h
View File

@@ -213,9 +213,9 @@ static inline int hpage_nr_pages(struct page *page)
}
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(struct mm_struct *mm)
}
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;
}

12
include/linux/mm.h
View File

@@ -2536,16 +2536,8 @@ static inline vm_fault_t vmf_error(int err)
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 */