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Mon, 14 Jul 2025 00:34:34 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.9]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 85EAB30001A1; Mon, 14 Jul 2025 00:34:21 +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 v9 08/14] khugepaged: skip collapsing mTHP to smaller orders Date: Sun, 13 Jul 2025 18:32:01 -0600 Message-ID: <20250714003207.113275-9-npache@redhat.com> In-Reply-To: <20250714003207.113275-1-npache@redhat.com> References: <20250714003207.113275-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Rspamd-Queue-Id: AB806140002 X-Stat-Signature: hsy5miq9g8qpwpwfxs8h7fbxgg9iur7o X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1752453345-563826 X-HE-Meta: U2FsdGVkX1+9m6XkMUjO9hb2hBRn2yfTFoAvWvO5zdM4JjJkLZLpQ8VPhpr33LCGfBkPu1IRr08EwquhTRQgO/LeEYiqg8msNO5yW0Uc/c8yE7i6toDn1Q+4sIHkFgm49fw8YKKBYh0hiq6yd/HppJNeAJilVPmiJTWa05lnNOOtzwbfzHSUgQKHEbNlFQHpOrvdaSwxdt6Y9FiiG48QmuDEYWRfKFRKxovHg7h6FlHzhEbLko1hCtXEhQuDfAKVIElxo6A6Tb0E/YfzC5kFv6UCpcGElwSLmy6MYR2sDY/3kENZLjUvm6xQpSrUx+M3WdHYVBRGwuWRIAOmi6X1aZYEPESn2UFvhJg84TdJin4WVqJfaIhS83HZ0cNhy0NyHK5SrofnBy90IbYW7kwA6J6STQuNvHQ2Y8r3xdQ8BTvaXecS6w/PiTdoc3LZ9Lxc0mqvudY9j5PnJvYC7iF50OXCHNVUPH+mooY3KGzQBTy5y8PizW7EclynIEMnlAM9LBL8J7piF7J+h1d9rSviOVL1Q8U4LOcj+xy3MpepGdcXMTP3RkfHdPB8wEg5G6WNOu+p/NlV/31PBby9aiacJQgHNVKBea38g6iwlJcyPF76LtcN0mBR3WGVqXoHNWYAfiqZv26FqJotsQJTp/Vd3y+++N0eTI5iWh6QtVBf7AlqaAs1VZqL1BSB8unQ3Fb2AUNE6pP++J7czR2IbwAwUuKPpTbxhx7SxOQAa/i8nt+5JJ7Hx5l7HLfSNFj3Gir5fbyqvw9mzGEaT6jHVPZ/uOLIrEFVUFGzLM5qbmRNVQ5h5WGOsIf39C+58+lkKmoQw71cvCK34Q0fDb6X7W1HwuYlQf2EIYsaA9Uc/o6wXA61YrbqajEEa9ewDVsZ2GQ1bjyvNVPFilu6tAHUyZMea/kZjldtPlrZ7HnfugUThhM4zGyzTZ5EVKYf+BYaoOXNylF0RsftOdgzR1vTDyQ +zlQl6IJ 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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: Baolin Wang Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Nico Pache --- mm/khugepaged.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5d7c5be9097e..a701d9f0f158 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -612,7 +612,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, folio = page_folio(page); VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); - /* See hpage_collapse_scan_pmd(). */ + if (order != HPAGE_PMD_ORDER && folio_order(folio) >= order) { + result = SCAN_PTE_MAPPED_HUGEPAGE; + goto out; + } + + /* See khugepaged_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { ++shared; if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged && -- 2.50.0