The patch titled
Subject: mm, THP, swap: support to split THP in swap cache
has been added to the -mm tree. Its filename is
mm-thp-swap-support-to-split-thp-in-swap-cache.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-swap-support-to-split-thp-in-swap-cache.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-swap-support-to-split-thp-in-swap-cache.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm, THP, swap: support to split THP in swap cache
This patch enhances split_huge_page_to_list() to work properly for the THP
(Transparent Huge Page) in the swap cache during swapping out.
This is used for delaying splitting the THP during swapping out. Where
for a THP to be swapped out, we will allocate a swap cluster, add the THP
into the swap cache, then split the THP. The page lock will be held
during this process. So in the code path other than swapping out, if the
THP need to be split, the PageSwapCache(THP) will be always false.
Link: http://lkml.kernel.org/r/20170328053209.25876-9-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Ebru Akagunduz <ebru.akagunduz@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff -puN mm/huge_memory.c~mm-thp-swap-support-to-split-thp-in-swap-cache mm/huge_memory.c
--- a/mm/huge_memory.c~mm-thp-swap-support-to-split-thp-in-swap-cache
+++ a/mm/huge_memory.c
@@ -2185,7 +2185,7 @@ static void __split_huge_page_tail(struc
* atomic_set() here would be safe on all archs (and not only on x86),
* it's safer to use atomic_inc()/atomic_add().
*/
- if (PageAnon(head)) {
+ if (PageAnon(head) && !PageSwapCache(head)) {
page_ref_inc(page_tail);
} else {
/* Additional pin to radix tree */
@@ -2196,6 +2196,7 @@ static void __split_huge_page_tail(struc
page_tail->flags |= (head->flags &
((1L << PG_referenced) |
(1L << PG_swapbacked) |
+ (1L << PG_swapcache) |
(1L << PG_mlocked) |
(1L << PG_uptodate) |
(1L << PG_active) |
@@ -2258,7 +2259,11 @@ static void __split_huge_page(struct pag
ClearPageCompound(head);
/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
- page_ref_inc(head);
+ /* Additional pin to radix tree of swap cache */
+ if (PageSwapCache(head))
+ page_ref_add(head, 2);
+ else
+ page_ref_inc(head);
} else {
/* Additional pin to radix tree */
page_ref_add(head, 2);
@@ -2370,10 +2375,12 @@ int page_trans_huge_mapcount(struct page
/* Racy check whether the huge page can be split */
bool can_split_huge_page(struct page *page, int *pextra_pins)
{
- int extra_pins = 0;
+ int extra_pins;
/* Additional pins from radix tree */
- if (!PageAnon(page))
+ if (PageAnon(page))
+ extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
+ else
extra_pins = HPAGE_PMD_NR;
if (pextra_pins)
*pextra_pins = extra_pins;
@@ -2427,7 +2434,6 @@ int split_huge_page_to_list(struct page
ret = -EBUSY;
goto out;
}
- extra_pins = 0;
mapping = NULL;
anon_vma_lock_write(anon_vma);
} else {
_
Patches currently in -mm which might be from ying.huang@xxxxxxxxx are
mm-swap-fix-a-race-in-free_swap_and_cache.patch
mm-swap-fix-comment-in-__read_swap_cache_async.patch
mm-swap-improve-readability-via-make-spin_lock-unlock-balanced.patch
mm-swap-avoid-lock-swap_avail_lock-when-held-cluster-lock.patch
mm-swap-make-swap-cluster-size-same-of-thp-size-on-x86_64.patch
mm-memcg-support-to-charge-uncharge-multiple-swap-entries.patch
mm-thp-swap-add-swap-cluster-allocate-free-functions.patch
mm-thp-swap-add-get_huge_swap_page.patch
mm-thp-swap-support-to-clear-swap_has_cache-for-huge-page.patch
mm-thp-swap-support-to-add-delete-thp-to-from-swap-cache.patch
mm-thp-add-can_split_huge_page.patch
mm-thp-swap-support-to-split-thp-in-swap-cache.patch
mm-thp-swap-delay-splitting-thp-during-swap-out.patch
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