path: root/mm/nommu.c
diff options
authorKeith Busch <>2018-10-26 15:10:28 -0700
committerLinus Torvalds <>2018-10-26 16:38:15 -0700
commitdf06b37ffe5a442503b7095b77b0a970df515459 (patch)
tree2fdb301eba4b4c2240595040496096b3a6489c79 /mm/nommu.c
parent9fd61bc95130d4971568b89c9548b5e0a4e18e0e (diff)
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: Signed-off-by: Keith Busch <> Reviewed-by: Dan Williams <> Acked-by: Kirill A. Shutemov <> Cc: Dave Hansen <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/nommu.c')
1 files changed, 2 insertions, 4 deletions
diff --git a/mm/nommu.c b/mm/nommu.c
index e4aac33216ae..749276beb109 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1709,11 +1709,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
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;