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[70.53.202.134]) by smtp.gmail.com with ESMTPSA id af79cd13be357-910ba36e638sm231744885a.9.2026.05.14.05.14.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 May 2026 05:14:13 -0700 (PDT) Message-ID: Date: Thu, 14 May 2026 08:14:12 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/9] mm: thp: always enable mTHP support To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ziy@nvidia.com, lance.yang@linux.dev, 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, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org References: From: Luiz Capitulino In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: sc48XO6h6euifLHj9jcnxxTtRIBvrImilr8vyaPUslM_1778760855 X-Mimecast-Originator: redhat.com Content-Language: en-US, en-CA Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 1B4CB100019 X-Stat-Signature: dyo96yhgdbmpca7tmegrrri8hzp9e9jg X-Rspam-User: X-HE-Tag: 1778760856-289109 X-HE-Meta: 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 AMrXNm1C 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-05-14 02:35, Lorenzo Stoakes wrote: > -cc my previous kernel mail > > (Minor annoying reminder to update my email to ljs@kernel.org :P) Nah, my fault. I promise I updated your email now. > > On Fri, May 01, 2026 at 03:18:42PM -0400, Luiz Capitulino wrote: >> 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 08d0d3466664 ("Merge tag 'net-7.1-rc2' >> of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net") >> >> NOTE: I used Claude Code Opus 4.6 to *review* the series before >> posting. It did find one issue where a pgtable_has_pmd_leaves() >> check was missing when assining huge_shmem_orders_inherit in >> shmem_init(). >> >> v4 >> -- >> - Use 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 (9): >> docs: tmpfs: remove implementation detail reference >> 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: drop has_transparent_hugepage() usage >> 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 | 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 | 4 +-- >> drivers/dax/dax-private.h | 2 +- >> drivers/nvdimm/pfn_devs.c | 6 +++-- >> include/linux/huge_mm.h | 7 ------ >> include/linux/pgtable.h | 19 ++++++++++++-- >> init/main.c | 1 + >> mm/debug_vm_pgtable.c | 20 +++++++-------- >> mm/huge_memory.c | 25 +++++++++++++------ >> mm/memory.c | 11 +++++++- >> mm/shmem.c | 21 +++++++++------- >> 19 files changed, 93 insertions(+), 60 deletions(-) >> >> -- >> 2.53.0 >> >