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authorHuang Ying <ying.huang@intel.com>2017-07-06 15:37:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-06 16:24:31 -0700
commitb8f593cd0896b8b14c2b494a9776531b5cd54d98 (patch)
tree5338b7e5f1c1dc5aefb2473e780c27179f4d97da /mm/vmscan.c
parent0f0746589e4be071a8f890b2035c97c30c7a4e16 (diff)
mm, THP, swap: check whether THP can be split firstly
To swap out THP (Transparent Huage Page), before splitting the THP, the swap cluster will be allocated and the THP will be added into the swap cache. But it is possible that the THP cannot be split, so that we must delete the THP from the swap cache and free the swap cluster. To avoid that, in this patch, whether the THP can be split is checked firstly. The check can only be done racy, but it is good enough for most cases. With the patch, the swap out throughput improves 3.6% (from about 4.16GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case with 8 processes. The test is done on a Xeon E5 v3 system. The swap device used is a RAM simulated PMEM (persistent memory) device. To test the sequential swapping out, the test case creates 8 processes, which sequentially allocate and write to the anonymous pages until the RAM and part of the swap device is used up. Link: http://lkml.kernel.org/r/20170515112522.32457-5-ying.huang@intel.com Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for can_split_huge_page()] Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shaohua Li <shli@kernel.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 729e37f02de6..abaf0215a352 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1125,6 +1125,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
!PageSwapCache(page)) {
if (!(sc->gfp_mask & __GFP_IO))
goto keep_locked;
+ /* cannot split THP, skip it */
+ if (PageTransHuge(page) &&
+ !can_split_huge_page(page, NULL))
+ goto activate_locked;
if (!add_to_swap(page)) {
if (!PageTransHuge(page))
goto activate_locked;