Commit eb3b796a authored by Baolin Wang's avatar Baolin Wang Committed by Nanyong Sun
Browse files

mm: khugepaged: fix the incorrect statistics when collapsing large file folios 

mainline inclusion
from mainline-v6.12-rc4
commit d60fcaf00d752c52fdf566d4184e6d04d9d08879
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAXCD2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d60fcaf00d752c52fdf566d4184e6d04d9d08879

--------------------------------

Khugepaged already supports collapsing file large folios (including shmem
mTHP) by commit 7de856ffd007 ("mm: khugepaged: support shmem mTHP
collapse"), and the control parameters in khugepaged:
'khugepaged_max_ptes_swap' and 'khugepaged_max_ptes_none', still compare
based on PTE granularity to determine whether a file collapse is needed.
However, the statistics for 'present' and 'swap' in
hpage_collapse_scan_file() do not take into account the large folios,
which may lead to incorrect judgments regarding the
khugepaged_max_ptes_swap/none parameters, resulting in unnecessary file
collapses.

To fix this issue, take into account the large folios' statistics for
'present' and 'swap' variables in the hpage_collapse_scan_file().

Link: https://lkml.kernel.org/r/c76305d96d12d030a1a346b50503d148364246d2.1728901391.git.baolin.wang@linux.alibaba.com


Fixes: 7de856ffd007 ("mm: khugepaged: support shmem mTHP collapse")
Signed-off-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarBarry Song <baohua@kernel.org>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarNanyong Sun <sunnanyong@huawei.com>
parent 79f52fcb

mm/khugepaged.c

+2 −2
Original line number Diff line number Diff line
@@ -2266,7 +2266,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, 
			continue;



		if (xa_is_value(folio)) {

			++swap;

			swap += 1 << xas_get_order(&xas);

			if (cc->is_khugepaged &&

			    swap > khugepaged_max_ptes_swap) {

				result = SCAN_EXCEED_SWAP_PTE;
@@ -2318,7 +2318,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, 
		 * is just too costly...

		 */



		present++;

		present += folio_nr_pages(folio);



		if (need_resched()) {

			xas_pause(&xas);