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Fri, 22 May 2026 15:03:44 +0000 (UTC) Received: from p1.redhat.com (unknown [10.44.24.8]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D2D961800576; Fri, 22 May 2026 15:03:25 +0000 (UTC) From: Nico Pache To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, npache@redhat.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com, Usama Arif Subject: [PATCH mm-unstable v18 12/14] mm/khugepaged: avoid unnecessary mTHP collapse attempts Date: Fri, 22 May 2026 09:00:07 -0600 Message-ID: <20260522150009.121603-13-npache@redhat.com> In-Reply-To: <20260522150009.121603-1-npache@redhat.com> References: <20260522150009.121603-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -A8qjgqFXwhB9yTD_j9KslCoUUPmnopCFUeF0gkDfys_1779462224 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: 3aujp5xro5d4f8fwrcmmyjh549g5tcna X-Rspamd-Queue-Id: 178A22000C X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1779462233-825693 X-HE-Meta: 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 7xcC5JOB KG6J8wXTghILedSYS/WgXnFEuf1TMSxbJhqJOnUPeVxR5tlQD3OPKi3YpYiWmlLT1/PJSWTsmnNCBF5nAwtCKpE/0bBNS49WV3U2464ulCUYwvOfBOBpXr+/kLabG/yAGzNjhjedVkrFAkODp1cEnHWZYTVqyKUVNjVwPs8UwPtMR+TOBo4VYq4IpY6ZzqsLvBGg08LObMoXIXdCKRl6tCHwknuRndOw1SHzyoEmIOKX8bfdjjTcgA6Ar+RXmDZGBMpPukIHsOnaRlNpQehjTaqgGiyMPrJ/Bq4OR1OnihxuJ4eZ3ruxBNiejfU44N+dbihapvaSnli+S1fy0BGKvyMjdwfeu0rpZ+oMsrr9iWyhIcyi7Z3ulRRtiDF1OX/348myeNYWp/o6WBxWY6cCL+znNtwyqosPDPdXw+yJjrmmjS5FsenN6DmCK3Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: + case SCAN_PAGE_LAZYFREE: + goto next_order; + /* Cases where no further collapse is possible */ + default: + return collapsed; } } -- 2.54.0