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From: Lance Yang In-Reply-To: <65e201dd-10d6-43f6-8758-0fc313158fe7@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: b7fr7n9hsem4r54fyog99krzo79r3pgy X-Rspamd-Queue-Id: AF854A000B X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1780278922-401771 X-HE-Meta: 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 d874ReWM dXkj3vYgKaOUIKzlcNstvjcjV/LnCHcoCU/pe3S82nNuevRdLl+0CbY/OGU/AKzW5Lmpb8IAl/8IkNvNeMlewBe7H0AEIN1F7UIko2dlJRUEuUFbI8F8b4h8utazAwbswIuu3QoOmHOEBpYuhFxqmerxjVXXXFrVhv/9Bzr5wNCL7zm/vd3YSlH4h1ZbZEGv1a//tSv/2FHz9uLWm4OGIdB9O3Mqu7ZxJ7INNEp31Wbw0dQllyMuc/80jskc3iug12CHAAydat2p2Tf+jrPNR59KSqgqbxujmD7fW Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/6/1 04:02, David Hildenbrand (Arm) wrote: > 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 >>> Acked-by: Usama Arif >>> Acked-by: David Hildenbrand (Arm) >>> Signed-off-by: Nico Pache >>> --- >>> 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 .. :) Fair point. Just a nit, nevermind :)