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Thu, 26 Feb 2026 03:26:43 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.173]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8105B19560B6; Thu, 26 Feb 2026 03:26:34 +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.Howlett@oracle.com, lorenzo.stoakes@oracle.com, 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 Subject: [PATCH mm-unstable v15 11/13] mm/khugepaged: avoid unnecessary mTHP collapse attempts Date: Wed, 25 Feb 2026 20:26:31 -0700 Message-ID: <20260226032631.234234-1-npache@redhat.com> In-Reply-To: <20260226031741.230674-1-npache@redhat.com> References: <20260226031741.230674-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: j8GvNSYa4ExzfcwTenoaZTxMXGjby0ndBu4o6iizeEg_1772076404 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Queue-Id: 9B329180007 X-Stat-Signature: 1e7fkodmoe184k5nfoo3e197tg6qoehq X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1772076414-917340 X-HE-Meta: U2FsdGVkX18xvyVNlJboAhZGIOtJUM/QQOeKrqFDVlDrj7gXFr2RuM+s35Xjs72sMfBhdSl3LT7a9p6jsuT0WJDXYs0o+Jk0LUr2yjDztcYX3J2gF6X3wdajwPgaRseGj9MzPFF6svtVtTKsa8d2865jQoMqSDNjms1o5TLnLwaz4R8eQAY0h4UC0VyaDIcxYYfI+q3YxWA14WO/psoKa6riVLHvlWhXEUYyPmhV4NMr9FetuLY5UG/6/X4ePfO/9Dz88wCmUptIE/azoy7Y0sw1hLLBzLlQtWhvmbNS8M6/Ycci9C/PjNZoghVcoB5AbHTpin1FY/Age+jtpRdFbq2zISXEXGyx363msSTA4XA37775+JMj4WUd6Ec/AukdvOv7jRwQBPLini+U8P2IuhM4LLEBfLf+vKd9aX2xbn5tsY/MlDFLNisW8MbDqGFBGKrCl6APiMzGSmc82dtujD0icH2yYBSp/bceyXSsR+abpuqwPUbw5DqJ5jfxQmfjUmjLZIJlC6gXpaL6hDh4JSai2iWcjT5M0FPXyl9oTrya69tWvyivLgV4sbrt5Oug9VHniLdGwdYRmOPdCdY0vq4BIRpgZD3mawUE85hn/agD138YbZw3/L4VGhYSom1Phfw3rBIGs4NPvPuBr8R2t1G1gXFZFxr87lPv1w1+hl6EucScGqtCfVizgzeuDotZOoFKPg++B9WtdK9PohzUL7/5whEIrX45u7mwdrEo1eISQu0lZRmaZ+uPX55Xwm31ENd/AIkwID8LtdDtsd8RUrWCqKOq1Gwvz9XRmJhWM2i/xBDDlVt5Ol5vBS1EMrJUPL4qiOYl352awDE6vHedVhenXo/bAgOzK2d3aqWtKv0PqwqduQypVLzjLT5IB759dm+WTvksE+826VT9sBsL2ZcmSwr3M3LOLK4AtBoKbdSSGK/rVoUKFMGr+jqesTpS6fI6M1K0p/9So2DSgGk YB4uC/4M RWBY+R8uZSyxB4KAgZn60hc97Yn0XIPkd+8qetdXDnb6juxI05dsdmh0O//9zNDBmxFTMsgAWt7UNRcQBzgqyUezWjWnw0TxCVFzIvEJfsuwR8HhTjqgWjUzRFo2j/jpmwgsjqGLg56IhcRuBWKJO6gSLsh6vW0llayTPcwJ4zYS8bFlZEfBfFInhnlDdtDJlwAVWsypFwIyS68GTnoduLQ/4/IsymQ4AOU3oeeKNHW1OzAETvtGROZUiCPjcgXx+lUoUHJgEJj4N1tWDQyDb67Q2XwFpLikJCk03auFTlVyddZNWKvvPb1Lb3Tb62TIZ6rjL/Ni9+W90ZaOpUrRqy9FW0sG7LAAmPRWMUSko6t+r7pGSYhXMx91BNA== 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. Signed-off-by: Nico Pache --- mm/khugepaged.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 1c3711ed4513..388d3f2537e2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1492,9 +1492,42 @@ static int mthp_collapse(struct mm_struct *mm, unsigned long address, ret = collapse_huge_page(mm, collapse_address, referenced, unmapped, cc, mmap_locked, order); - if (ret == SCAN_SUCCEED) { + + switch (ret) { + /* Cases were we continue to next collapse candidate */ + case SCAN_SUCCEED: collapsed += nr_pte_entries; + fallthrough; + case SCAN_PTE_MAPPED_HUGEPAGE: continue; + /* Cases were 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_LRU: + 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: + goto next_order; + /* Cases were no further collapse is possible */ + case SCAN_CGROUP_CHARGE_FAIL: + case SCAN_COPY_MC: + case SCAN_ADDRESS_RANGE: + case SCAN_NO_PTE_TABLE: + case SCAN_ANY_PROCESS: + case SCAN_VMA_NULL: + case SCAN_VMA_CHECK: + case SCAN_SCAN_ABORT: + case SCAN_PAGE_ANON: + case SCAN_PMD_MAPPED: + case SCAN_FAIL: + default: + return collapsed; } } -- 2.53.0