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>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a023c5c..1e52b8f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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 */