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Thu, 06 Nov 2025 16:29:16 -0500 X-MC-Unique: iBqmsrqeMyW0bHI0o7um3Q-1 X-Mimecast-MFC-AGG-ID: iBqmsrqeMyW0bHI0o7um3Q_1762464555 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C4A801956063; Thu, 6 Nov 2025 21:29:14 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.65.101]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 8F25819560A7; Thu, 6 Nov 2025 21:29:13 +0000 (UTC) From: Luiz Capitulino To: david@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: [RFC 00/10] mm: thp: always enable mTHP support Date: Thu, 6 Nov 2025 16:28:47 -0500 Message-ID: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1A7CD40012 X-Stat-Signature: oiw7w64bn9ypqzui4b75xtzredwbe7eh X-Rspam-User: X-HE-Tag: 1762464560-334036 X-HE-Meta: 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 XqwcW0v8 yhpaOWPn0sC2stdoPyEpXSySdMah2MGMJ8Vx7xOllttCOBnj4a8zPOamY34/2N91LhmL0W+8jr+tOPJ/IiCV8rASKdI0BipPxBIU4H9kEGdhn02O4ChUUZtz8xWGKm40vLqrUSgCN4cUE0n7DJBRF++uwCB+0uVHzUmSQmi96ssRchAXr4ubjp+IOj5FRbCjeq0rY6pYtBoKvX09Awo8hMUwcjdmI9RpUoRZKD9EfO6jjPNKM5lYjEjfuNsxj/KdVSXS+iRFFNtrMKEQ= 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: Today, if an architecture implements has_transparent_hugepage() and the CPU lacks support for PMD-sized pages, the THP code disables all THP, including mTHP support. In addition, the kernel lacks a well defined API to check for PMD-sized page support. It currently relies on has_transparent_hugepage() and thp_disabled_by_hw(), but they are not well defined and are tied to THP support. This series addresses both issues by introducing a new well defined API to query PMD-sized page support: pgtable_has_pmd_leaves(). Using this new helper, we ensure that mTHP remains enabled even when the architecture or CPU doesn't support PMD-sized pages. An important detail is that we need to do the same refactoring for has_transparent_pud_hugepage(). I actually have patches for this one too, I'm not including them here because I want to get some initial feedback on the general approach first (and maybe it's better to do that in a separate series). Thanks to David Hildenbrand for suggesting this improvement and for providing guidance (all bugs and misconcentpions are mine). Luiz Capitulino (10): docs: tmpfs: remove implementation detail reference mm: introduce pgtable_has_pmd_leaves() drivers: dax: use pgtable_has_pmd_leaves() drivers: i915 selftest: use pgtable_has_pmd_leaves() drivers: nvdimm: use pgtable_has_pmd_leaves() mm: debug_vm_pgtable: use pgtable_has_pmd_leaves() treewide: rename has_transparent_hugepage() to arch_has_pmd_leaves() mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() mm: thp: always enable mTHP support mm: thp: x86: cleanup PSE feature bit usage Documentation/filesystems/tmpfs.rst | 5 ++--- arch/mips/include/asm/pgtable.h | 4 ++-- arch/mips/mm/tlb-r4k.c | 4 ++-- arch/powerpc/include/asm/book3s/64/hash-4k.h | 2 +- arch/powerpc/include/asm/book3s/64/hash-64k.h | 2 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 10 +++++----- arch/powerpc/include/asm/book3s/64/radix.h | 2 +- arch/powerpc/mm/book3s64/hash_pgtable.c | 4 ++-- arch/s390/include/asm/pgtable.h | 4 ++-- arch/x86/include/asm/pgtable.h | 6 ------ arch/x86/include/asm/pgtable_32.h | 6 ++++++ drivers/dax/dax-private.h | 2 +- .../gpu/drm/i915/gem/selftests/huge_pages.c | 2 +- drivers/nvdimm/pfn_devs.c | 4 ++-- include/linux/huge_mm.h | 7 ------- include/linux/pgtable.h | 14 +++++++++++-- mm/debug_vm_pgtable.c | 20 +++++++++---------- mm/huge_memory.c | 13 ++++++------ mm/memory.c | 12 ++++++++++- mm/shmem.c | 8 ++++---- 20 files changed, 72 insertions(+), 59 deletions(-) -- 2.51.1