[PATCH v8 09/15] khugepaged: avoid unnecessary mTHP collapse attempts
From: Nico Pache <npache@redhat.com>
Date: 2025-07-02 06:00:56
Also in:
linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - thp (transparent huge page), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds
There are cases where, if an attempted collapse fails, all subsequent orders are guaranteed to also fail. Avoid these collapse attempts by bailing out early. Signed-off-by: Nico Pache <npache@redhat.com> --- mm/khugepaged.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 61d2b3ebc7ac..50e1d7ef7e6d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c@@ -1358,6 +1358,23 @@ static int khugepaged_scan_bitmap(struct mm_struct *mm, unsigned long address, collapsed += (1 << order); continue; } + /* + * Some ret values indicate all lower order will also + * fail, dont trying to collapse smaller orders + */ + if (ret == SCAN_EXCEED_NONE_PTE || + ret == SCAN_EXCEED_SWAP_PTE || + ret == SCAN_EXCEED_SHARED_PTE || + ret == SCAN_PTE_NON_PRESENT || + ret == SCAN_PTE_UFFD_WP || + ret == SCAN_ALLOC_HUGE_PAGE_FAIL || + ret == SCAN_CGROUP_CHARGE_FAIL || + ret == SCAN_COPY_MC || + ret == SCAN_PAGE_LOCK || + ret == SCAN_PAGE_COUNT) + goto next; + else + break; } next:
--
2.49.0