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Tue, 19 Aug 2025 09:45:16 -0400 X-MC-Unique: JMbLXzPAN8e6Zz9iKHx7DA-1 X-Mimecast-MFC-AGG-ID: JMbLXzPAN8e6Zz9iKHx7DA_1755611109 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6015D180034A; Tue, 19 Aug 2025 13:45:08 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.137]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EF37F19560AB; Tue, 19 Aug 2025 13:44:50 +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, kirill.shutemov@linux.intel.com, 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 Subject: [PATCH v10 07/13] khugepaged: skip collapsing mTHP to smaller orders Date: Tue, 19 Aug 2025 07:41:59 -0600 Message-ID: <20250819134205.622806-8-npache@redhat.com> In-Reply-To: <20250819134205.622806-1-npache@redhat.com> References: <20250819134205.622806-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CEE0618000A X-Stat-Signature: u5qbm5hqoydsj913tg5xci8hoqfiuzos X-Rspam-User: X-HE-Tag: 1755611120-684181 X-HE-Meta: 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 dilTTs7Q 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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/ Acked-by: David Hildenbrand Reviewed-by: Baolin Wang 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 1ad7e00d3fd6..6a4cf7e4a7cc 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -611,6 +611,15 @@ 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; -- 2.50.1