On 5/31/26 09:31, Lance Yang wrote: > > On Fri, May 22, 2026 at 09:00:07AM -0600, Nico Pache wrote: >> 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. >> >> Reviewed-by: Lorenzo Stoakes <[email protected]> >> Acked-by: Usama Arif <[email protected]> >> Acked-by: David Hildenbrand (Arm) <[email protected]> >> Signed-off-by: Nico Pache <[email protected]> >> --- >> mm/khugepaged.c | 24 +++++++++++++++++++++++- >> 1 file changed, 23 insertions(+), 1 deletion(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index d3d7db8be26c..15b7298bc225 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -1535,9 +1535,31 @@ static int mthp_collapse(struct mm_struct *mm, struct >> vm_area_struct *vma, >> collapse_address = address + offset * PAGE_SIZE; >> ret = collapse_huge_page(mm, collapse_address, >> referenced, >> unmapped, cc, order); >> - if (ret == SCAN_SUCCEED) { >> + >> + switch (ret) { >> + /* Cases where we continue to next collapse candidate */ >> + case SCAN_SUCCEED: >> collapsed += nr_ptes; >> + fallthrough; >> + case SCAN_PTE_MAPPED_HUGEPAGE: >> continue; >> + /* Cases where lower orders might still succeed */ >> + case SCAN_LACK_REFERENCED_PAGE: >> + case SCAN_EXCEED_NONE_PTE: >> + case SCAN_EXCEED_SWAP_PTE: >> + case SCAN_EXCEED_SHARED_PTE: >> + case SCAN_PAGE_LOCK: >> + case SCAN_PAGE_COUNT: >> + case SCAN_PAGE_NULL: >> + case SCAN_DEL_PAGE_LRU: >> + case SCAN_PTE_NON_PRESENT: >> + case SCAN_PTE_UFFD_WP: >> + case SCAN_ALLOC_HUGE_PAGE_FAIL: > > Nit: shouldn't SCAN_CGROUP_CHARGE_FAIL go with SCAN_ALLOC_HUGE_PAGE_FAIL > here? > > If charging the current order fails, a smaller order might still fit :)
I think the reasoning was here, that if we are already that close to our mem limit, we should just give up instead of trying to squeeze it in .. :) -- Cheers, David
