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Fri, 29 May 2026 10:56:07 -0400 X-MC-Unique: muPWJ1WFPG2ETWNc1CObWw-1 X-Mimecast-MFC-AGG-ID: muPWJ1WFPG2ETWNc1CObWw_1780066564 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 600E018002E4; Fri, 29 May 2026 14:56:02 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.64.88]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3376530001BB; Fri, 29 May 2026 14:55:57 +0000 (UTC) From: Luiz Capitulino To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ziy@nvidia.com, lance.yang@linux.dev Cc: corbet@lwn.net, tsbogend@alpha.franken.de, maddy@linux.ibm.com, mpe@ellerman.id.au, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, x86@kernel.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, ira.weiny@intel.com, hughd@google.com, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, yintirui@huawei.com, ljs@kernel.org Subject: [PATCH v5 00/14] mm: thp: always enable mTHP support Date: Fri, 29 May 2026 10:55:18 -0400 Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: zyEXbg9tJREcXx5WeaRzbT7ZF8iZlhU2Rr9-_-22hUE_1780066564 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: jqck9ai6id5g1e3jcr84e44o1uaz1o1h X-Rspamd-Queue-Id: 913FB14000D X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1780066571-954805 X-HE-Meta: U2FsdGVkX1+XPtC39FQyT2sg3zNgsmtMRlql9/NzD4h/tm1TzH3Vwww/t0TT/f2CFoqTMCM9O135irPF0tus8qxG/cTIewQZgowREk2nEO4MO/oubwGqM9vDrogQSORYkH0R/UPb+Aj+BzQpWFYrImevjc6HpImU/iiXmmdTgEGOIcSp42xohJWtVJq+LJzzqFOnCg7dEkmHgDzA7SeII+K29GlvewFHCHJtCoIftk0KB7WJ9zMGGkimtzNBYWYVXbX+60T0j4NDGMl0J9ITqd/xrZTVZTN3RvzPsJ0YrWZCizZIez/fjBblxpO3dyBLkur2CyKHaUhNK7geuau4uXf/PbWl4tgEjXxFAjstDRAddYwPJlHqbf+XAv4A84TgwIBY0FBbam+fSYQi0BhggR3BthYqPwBc+NPAIE2ZvT1hkElpp6QwQVtbJ5/2uDrLjd9qHHhedViejcaSnFsxaQEDc+lIFa64HgkVjr6WGr5MDWWNKgu5LqK+r5Ly4efV6A84T8TMXsey4n44zDyylXZKAAcuZDwz/lQw+DAWDCPYUGLOojP78igwdHvSTesQUL7O/A5N4iyaq4Kq18VBn13aqmyFUbAanU4JnXGSdzLG5We7+Ae6nm7Bl9NUTUDepzAzRl7bWWTq21H5MXR5P4FMCaTwa3OaVPEqOFOJNzIB5BHur8lS/Lb3K1zY1GWO8bd8GjfM/hAw5PtrnxtARjY++g0LHVs1dNpl1RbEYBtdNCf8ll/R2Z7xOGAR1pDNR0FaeHVRTYrgv3StQicSTWIN1h+8HrDGL+q7m9xkeOnBn82fYh0/Cy1DX2o0u/5x3RfHaVzANc3WaagnFqenLTFo/+cxNKdLhjSYeIryd6t2eMoz1epB6/5TPYY5cxjFGD4WCLsOtmGdIiBZvHVuLzwf0b2RFlIRf+j1lTJDzqZ3d04AfVlBUg8qgPi9qMpuewCzxTYZU7PGAI1G/zm DqrtoEnM kP20X0x4a5So5WJ3BxfqvahECe8b1Uf7g/LpoJyb4WzVvNrwB/4QdPYViljWmoT9w9/zNGthne8Rt66cyMQKnqer9zxHniRQicaXmBE9TQFSYUzjad1+f8FmZAvRtsazAv334pl471APw16cRq0VAmYwridY2fPrL4qovsKpT91eVhUZjuzGRBHkz7UE4erMdIoMbCd/VyzDgagN88I+gVmix2gIfp3AfCjB9wMo/9My7C+P27dDeiI++lYglOhdcZlD91c8lmTDdH/SYA6lzau0J31ph0clbieVn9cwGsXpQp0IscE5HYJ0RNlO454EgXd4r7fn1TjipxM/oYL5cj5p1ZaBQ+dnyod4cHvsjT/l4uUE= 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. 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. Thanks to David Hildenbrand for suggesting this improvement and for providing guidance (all bugs and misconceptions are mine). This applies to Linus tree eb3f4b7426cf ("Merge tag 'nfsd-7.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux") NOTE: I used Claude Code Opus 4.6 to review the series before posting. No issues found. v5 -- - Moved init_arch_has_pmd_leaves() to mm_core_init() (David) - Renamed init_arch_has_pmd_leaves() to pgtable_leaf_support_init() (Lance) - Added new patch changing shmem_getattr() to set blksize according to highest supported THP order (Baolin) - Added new patches to move has_transparent_hugepage() out of CONFIG_TRANSPARENT_HUGEPAGE guards (Sashiko) - shmem_allowable_huge_orders(): rename variable and only disable PMD_ORDER (David) - Added to include/linux/pgtable.h (Sashiko) - Added new tags and removed Reviewed-by from changed patches v4 -- - Used static key for pgtable_has_pmd_leaves() API (Lance) - Moved shmem pgtable_has_pmd_leaves() check to shmem_allowable_huge_orders() (Baolin) - Default pgtable_has_pmd_leaves() implementation to IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE) (Zi) - Dropped patch “mm: thp: x86: cleanup PSE feature bit usage” (Dave) v3 -- - Rebased on top of latest Linus tree - Removed i915 patch as driver dropped has_transparent_hugepage() usage - Moved init_arch_has_pmd_leaves() call in start_kernel() to avoid conflict with early_param handlers clearing CPU feature flags - Fixed build error with CONFIG_MMU=n (kernel test robot) - Fixed huge_anon_orders_inherit default setting when !pgtable_pmd_leaves() (Baolin) - Small commit changelog improvements v2 -- - Added support for always enabling mTHPs for shmem (Baolin) - Improved commits changelog & added reviewed-by v1 -- - Call init_arch_has_pmd_leaves() from start_kernel() - Keep pgtable_has_pmd_leaves() calls tied to CONFIG_TRANSPARENT_HUGEPAGE (David) - Clear PUD_ORDER when clearing PMD_ORDER (David) - Small changelog improvements (David) - Rebased on top of latest mm-new Luiz Capitulino (14): docs: tmpfs: remove implementation detail reference mm: shmem: shmem_getattr(): set blksize to highest supported THP order mm: introduce pgtable_has_pmd_leaves() drivers: dax: use pgtable_has_pmd_leaves() drivers: nvdimm: use pgtable_has_pmd_leaves() mm: debug_vm_pgtable: use pgtable_has_pmd_leaves() mm: shmem: allow THP support determination at folio allocation time s390: move has_transparent_hugepage() out of THP guard powerpc: move has_transparent_hugepage() out of THP guard mips: move has_transparent_hugepage() out of THP guard x86: move has_transparent_hugepage() out of THP guard treewide: introduce arch_has_pmd_leaves() mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() mm: thp: always enable mTHP support Documentation/filesystems/tmpfs.rst | 5 ++-- arch/mips/include/asm/pgtable.h | 6 ++-- arch/mips/mm/tlb-r4k.c | 8 ++--- 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 | 18 ++++++------ arch/powerpc/include/asm/book3s/64/radix.h | 14 ++++----- arch/powerpc/mm/book3s64/hash_pgtable.c | 8 ++--- arch/s390/include/asm/pgtable.h | 6 ++-- arch/x86/include/asm/pgtable.h | 12 ++++---- drivers/dax/dax-private.h | 2 +- drivers/nvdimm/pfn_devs.c | 6 ++-- include/linux/huge_mm.h | 7 ----- include/linux/pgtable.h | 20 +++++++++++-- mm/debug_vm_pgtable.c | 20 ++++++------- mm/huge_memory.c | 27 ++++++++++++----- mm/memory.c | 11 ++++++- mm/mm_init.c | 1 + mm/shmem.c | 29 ++++++++++++------- 19 files changed, 120 insertions(+), 84 deletions(-) -- 2.54.0