The patch titled
Subject: mm: khugepaged: fix the incorrect statistics when collapsing large file folios
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-khugepaged-fix-the-incorrect-statistics-when-collapsing-large-file-folios.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-fix-the-incorrect-statistics-when-collapsing-large-file-folios.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: khugepaged: fix the incorrect statistics when collapsing large file folios
Date: Mon, 14 Oct 2024 18:24:44 +0800
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@xxxxxxxxxxxxxxxxx
Fixes: 7de856ffd007 ("mm: khugepaged: support shmem mTHP collapse")
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Barry Song <baohua@xxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-fix-the-incorrect-statistics-when-collapsing-large-file-folios
+++ a/mm/khugepaged.c
@@ -2252,7 +2252,7 @@ static int hpage_collapse_scan_file(stru
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;
@@ -2299,7 +2299,7 @@ static int hpage_collapse_scan_file(stru
* is just too costly...
*/
- present++;
+ present += folio_nr_pages(folio);
if (need_resched()) {
xas_pause(&xas);
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
mm-khugepaged-fix-the-incorrect-statistics-when-collapsing-large-file-folios.patch
mm-shmem-fix-khugepaged-activation-policy-for-shmem.patch
