The patch titled
Subject: mm/thp: decrease nr_thps in file's mapping on THP split
has been added to the -mm tree. Its filename is
mm-thp-decrease-nr_thps-in-files-mapping-on-thp-split.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-thp-decrease-nr_thps-in-files-mapping-on-thp-split.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-decrease-nr_thps-in-files-mapping-on-thp-split.patch
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------------------------------------------------------
From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Subject: mm/thp: decrease nr_thps in file's mapping on THP split
Decrease nr_thps counter in file's mapping to ensure that the page cache
won't be dropped excessively on file write access if page has been
already splitted.
I've tried a test scenario, where one runs a big binary, kernel remaps it
with THPs, then one forces THP split with
/sys/kernel/debug/split_huge_pages. During any further open of that
binary with O_RDWR or O_WRITEONLY kernel drops page cache for it, because
of non-zero thps counter.
Link: https://lkml.kernel.org/r/20211012120237.2600-1-m.szyprowski@xxxxxxxxxxx
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Fixes: 09d91cda0e82 ("mm,thp: avoid writes to file with THP in pagecache")
Fixes: 06d3eff62d9d ("mm/thp: fix node page state in split_huge_page_to_list()")
Acked-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: <sfoon.kim@xxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/huge_memory.c~mm-thp-decrease-nr_thps-in-files-mapping-on-thp-split
+++ a/mm/huge_memory.c
@@ -2700,12 +2700,14 @@ int split_huge_page_to_list(struct page
if (mapping) {
int nr = thp_nr_pages(head);
- if (PageSwapBacked(head))
+ if (PageSwapBacked(head)) {
__mod_lruvec_page_state(head, NR_SHMEM_THPS,
-nr);
- else
+ } else {
__mod_lruvec_page_state(head, NR_FILE_THPS,
-nr);
+ filemap_nr_thps_dec(mapping);
+ }
}
__split_huge_page(page, list, end);
_
Patches currently in -mm which might be from m.szyprowski@xxxxxxxxxxx are
mm-thp-decrease-nr_thps-in-files-mapping-on-thp-split.patch
