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Thu, 11 Sep 2025 23:30:49 -0400 X-MC-Unique: iImcHlBZOBqp8n-HOYvhmg-1 X-Mimecast-MFC-AGG-ID: iImcHlBZOBqp8n-HOYvhmg_1757647839 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A3EDD1953943; Fri, 12 Sep 2025 03:30:39 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.80.28]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0FD5A180035E; Fri, 12 Sep 2025 03:30:29 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de Subject: [PATCH v11 08/15] khugepaged: skip collapsing mTHP to smaller orders Date: Thu, 11 Sep 2025 21:28:03 -0600 Message-ID: <20250912032810.197475-9-npache@redhat.com> In-Reply-To: <20250912032810.197475-1-npache@redhat.com> References: <20250912032810.197475-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 93C4CC000A X-Stat-Signature: cwi1tja9z5u87otysh6yf3emubx9yahm X-Rspam-User: X-HE-Tag: 1757647854-569084 X-HE-Meta: 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 VYJHC40K 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some pages being unmapped. Skip these cases until we have a way to check if its ok to collapse to a smaller mTHP size (like in the case of a partially mapped folio). This patch is inspired by Dev Jain's work on khugepaged mTHP support [1]. [1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ Reviewed-by: Lorenzo Stoakes Reviewed-by: Baolin Wang Acked-by: David Hildenbrand Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Nico Pache --- mm/khugepaged.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 248947e78a30..ebcc0c85a0d6 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -610,6 +610,15 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, folio = page_folio(page); VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); + /* + * TODO: In some cases of partially-mapped folios, we'd actually + * want to collapse. + */ + if (order != HPAGE_PMD_ORDER && folio_order(folio) >= order) { + result = SCAN_PTE_MAPPED_HUGEPAGE; + goto out; + } + /* See collapse_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { ++shared; -- 2.51.0