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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1775723402; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TG3Qdmc3lNsKjHzcIFMYLHvMSiJZlrsl5sNm+q7Fpf4=; b=gKn52ztF2FP3C+TwXjdoMyA1rNNVY9jZ4UKAWphquuDJP/cRFaH4VO9IRBArnsN7TDAdtr Y1/36Y8WzjmU9eE4JBYNIOyEepZ+djE9yYdlZP3LRIejQXBAOh3YIjVdcDEyLokHaXJB2+ svMCUveneaKphq4wfX2ie8yFWmQJSnI= From: Lance Yang To: luizcap@redhat.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, ljs@kernel.org, Liam.Howlett@oracle.com, npache@redhat.com, dev.jain@arm.com, Lance Yang Subject: Re: [PATCH v3 00/10] mm: thp: always enable mTHP support Date: Thu, 9 Apr 2026 16:29:36 +0800 Message-Id: <20260409082936.50302-1-lance.yang@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 38C501C000C X-Stat-Signature: uwk677mnfmemnc4snex8yeenegigpkq7 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1775723404-341989 X-HE-Meta: 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 jOk3uU+X v7UvRIusGt1E/0rpDFHDJLsaMrV/3QJdOwpruvIvYJeJFf2poJDxkmQoa2L64XbNrT6HHL7WlaAu35CB8Ugj3JEJh54Ijpwp/HBH2GdMNgipA8DCbfS5PSL3TYoou8o/6kLD+NuOqhdeAMOrub5hXvasPVRPcJZKes9lTSwA5bNc1rYL17LZS4bEqh2HtgpiyV7coilc86P722ol+tijlUWTN4LSRGGPhopvrWqkGV72IowE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: +Cc THP Some folks seem to be missing from CC for this series. Please run scripts/get_maintainer.pl; it's your friend :) Thanks, Lance On Wed, Apr 08, 2026 at 04:22:55PM -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 bfe62a454542 ("Merge tag 'soc-fixes-7.0-2' >of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc"). > >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 (10): > 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: 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 +- > 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 | 15 +++++++------- > mm/memory.c | 10 +++++++++- > mm/shmem.c | 11 +++++----- > 20 files changed, 80 insertions(+), 60 deletions(-) > >-- >2.53.0 > >