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Sat, 03 Oct 2026 03:13:09 +0000 X-Mizu-Trace-ID: 60bba976d3c550d3 X-Migadu-Flow: FLOW_OUT 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, 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, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, 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, dev.jain@arm.com, usama.arif@linux.dev Subject: Re: [PATCH v8 14/14] mm: thp: always enable mTHP support Date: Sat, 3 Oct 2026 11:13:01 +0800 Message-ID: <20261003031301.48957-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <752f528f0fed5cdc9de12b54260b0495d4e5a6cb.1789695931.git.luizcap@redhat.com> References: <752f528f0fed5cdc9de12b54260b0495d4e5a6cb.1789695931.git.luizcap@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4363040007 X-Stat-Signature: p5hosanhq4rkwky6gacc1d68rfj5qxdb X-HE-Tag: 1790997195-22478 X-HE-Meta: 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 TlX0AoEN uobef+/U6oRYxQAtUQMN6vqffBH87FU0CNKT+62/G8qU0G6oKSlLLHhsAa7mnPWTc2pibPGy19zMcGQhYly/BZIMmY+Cn15bPXHi225U9kloJUipUZ2lejIwwNv4vVgJWsFVvQeCo19d0kb4WNRsBFHNa3HoILg3RUZWjKZNkndouTPYb+BJstKH5w4++1b64S+40507ZUmhoVT2BSdP8ppl86UQ7B8K1ibESF8wO6IM2nQ0IrtYHhz8Clh6Er0o3uEgP Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 17, 2026 at 09:45:35PM -0400, Luiz Capitulino wrote: >If PMD-sized pages are not supported on an architecture (ie. the >arch implements arch_has_pmd_leaves() and it returns false) then the >current code disables all THP, including mTHP. > >This commit fixes this by allowing mTHP to be always enabled for all >archs. When PMD-sized pages are not supported, its sysfs entry won't be >created and their mapping will be disallowed at page-fault time. > >Similarly, this commit implements the following changes for shmem in >shmem_allowable_huge_orders(): > > - Drop the pgtable_has_pmd_leaves() check so that mTHP sizes are > considered > - Filter out PMD and PUD orders from allowable orders when > PMD-sized pages are not supported by the CPU Nit: "and PUD" can go. David mentioned " There is no need to disable PUD-orders, as shmem does not support PUD-orders (unlike DAX). So you can keep it simpler here. " in v4 https://lore.kernel.org/all/ff7bcd65-d444-4da1-890e-75504303ec3f@kernel.org/ Cheers, Lance