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[70.53.202.134]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-517ef5d9031sm23333681cf.16.2026.06.11.11.00.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Jun 2026 11:00:12 -0700 (PDT) Message-ID: <47f9202b-71b1-41e7-8185-426beb9d4a2c@redhat.com> Date: Thu, 11 Jun 2026 14:00:11 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 00/14] mm: thp: always enable mTHP support 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, Andrew Morton 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, yintirui@huawei.com, ljs@kernel.org References: Content-Language: en-US, en-CA In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit [ Top posting ] Andrew, I wonder if it's time to add this series to mm-unstable so that it gets more testing? I (quickly) went through Sashiko's review and most are minor things (OK, there's one review comment that I want to better check, but still some testing in mm-unstable has more value). - Luiz On 2026-05-29 10:55, 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 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(-) >