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b=KjWgS8Yi09HktsXwEj0X32oeSUm6hFNnKPxjKolb+3/FOZDdFTNBDTcPbjJLfYKD/ jincMbatuAl7HplWQuRJXke29Q+vKGYqaHeYwrOL2RwLPY4owoDj/SuEXK/hVpgUEx pC/N0XL1ZfEIecHsuSgjre8i5C6HfqAIeXWaklVQ= Date: Sun, 3 May 2026 08:02:36 -0700 From: Andrew Morton To: Luiz Capitulino 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, lorenzo.stoakes@oracle.com Subject: Re: [PATCH v4 0/9] mm: thp: always enable mTHP support Message-Id: <20260503080236.4ea7f3fec0e5788d50113599@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 4DE562000D X-Stat-Signature: h74i5gjz6e5gy339518cxe4tf9t19mtz X-Rspam-User: X-HE-Tag: 1777820564-213156 X-HE-Meta: U2FsdGVkX1/oRI8kGs/G85aeeBOw3d3CoEek7VGT1D8xpepKQtNaPrt6mOTkvu4cPzUqhsUDbRDDtMOLv8MpGf51GlVzAjj5lAO9kRRyAruKyz16FKkbTzfATfGjLa/Hhko5qn9XgDlejMWdPAyGB4FXpJgNb+ZHVvdRZNKF39XF+3L7b4o9CFxRMsuLLOK99mjMWdJm8JqNLCi658I3uYW4Aja4JcD1eCdTOXW1UGYCoeCT/ZhtM7Qtfkg0UJRJ1eMMDvM981aqLc5niGiUAW2+26FUIKdqbDhCkOIEydoku/H7drp762H7fe0pySPL86ibzwodZcrDq51SMopaYW4GzUyX5FevqZ9SzLFQkUk+XVHop/m2SPwSvehMRjlV20Up+HcOiUYAM+4aMUxTznNxkrsrpauCulGSo6o3PpDNj/d3u14fH5ss+lRsPwb3gwoCCeOu2cfl3ri13pTI7bW31vfaWPsR1uu5BJDwH2kSqF57erCmCnW6Jn98B5u4MfGzqVZYLzQTdUDARsMz5HrtHoEW0rgwTfiv1fHf3VM4wBJZU8YZwPG6yo5uHe266+qjoTuhVz7IDHnL0dbACxmG9bjBk2gtFbIRnYZjQ4BQPw+jcrYwFjZfOS/YfVynqXr7YHiOUyNfmnSN5khpkiQ2iEzK7zd1kiHAmw0FCLrYEHfRYOF98yIe6CFp8DGKsL79eRr3YiNgyUisLAc2x+kDGJVFz0aoZtM0ZfD/b36HyeWXXkbSUUHZU4E2+lAy1TMrQ6mtF0NuGem29wIR00NOlhGRz67/DeYypumljdVYgSW0iAsy8Bw+ESr7PVY8u/EovPiOnn8cefpxgVyQm3YfAVRjPyNBvlshY2PmDG/YNYmsHMU+487h1IaNT7sdOFmWiGoks82y8cc5L6leT+eWNVqNObyVGOfo/zcn9eYyJematDEX/TGL/I2gERPC1YGnbVdf7FnnG+SmGlk VoqUxj1p XVUDw09rIXobL4XEE6XGgaxlWhozp1ippQIZeKb+y5n4b62AQ5VE8yrOpzJepxn+5c0F0AZkdDvVPqUklw/5YWlrWM5H0s27KyTMoYgz3XxgjouRixV2Ypj4xwrDfkUMdwBfs6UcoKICs6NsvqBFHOj3JKD1K99oS1GxHOrjay/Ly5Ln3hv29Lt23wuHoJ+FDwgICSMvMEyrVQiwv//4SRCFszaBXrUcQic5fiJdQClnlmYQG+GcJjW9NklwKeDPQFYbdL5ycGSoQwaiEX99UghStMIJ+TsgJpjG19i6RO/zVCu0hjlyl2CRWtjXQDLgkN9oaa5YXlTRzkA/frtgsJ5Xgn/9LDutnmlTF Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 1 May 2026 15:18:42 -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(). Thanks. Sashiko found a few other things to ask about: https://sashiko.dev/#/patchset/cover.1777663129.git.luizcap@redhat.com