On 2/3/21 11:28 PM, John Hubbard wrote:

On 2/3/21 2:00 PM, Joao Martins wrote:

quoted

Rather than decrementing the head page refcount one by one, we
walk the page array and checking which belong to the same
compound_head. Later on we decrement the calculated amount
of references in a single write to the head page. To that
end switch to for_each_compound_head() does most of the work.

set_page_dirty() needs no adjustment as it's a nop for
non-dirty head pages and it doesn't operate on tail pages.

This considerably improves unpinning of pages with THP and
hugetlbfs:

- THP
gup_test -t -m 16384 -r 10 [-L|-a] -S -n 512 -w
PIN_LONGTERM_BENCHMARK (put values): ~87.6k us -> ~23.2k us

- 16G with 1G huge page size
gup_test -f /mnt/huge/file -m 16384 -r 10 [-L|-a] -S -n 512 -w
PIN_LONGTERM_BENCHMARK: (put values): ~87.6k us -> ~27.5k us

Signed-off-by: Joao Martins <redacted>
---
  mm/gup.c | 29 +++++++++++------------------
  1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 4f88dcef39f2..971a24b4b73f 100644
--- a/mm/gup.c
+++ b/mm/gup.c

@@ -270,20 +270,15 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
  				 bool make_dirty)
  {
  	unsigned long index;
-
-	/*
-	 * TODO: this can be optimized for huge pages: if a series of pages is
-	 * physically contiguous and part of the same compound page, then a
-	 * single operation to the head page should suffice.
-	 */

Great to see this TODO (and the related one below) finally done!

Everything looks correct here.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

Thank you!

	Joao