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b=JoqGxTpsdH4z489Esvh4AzxVwhzhPfJhljlsDpfmCTo46a8h+2AeB9bm501UUlrLn pWqBUaihIoZsWn0uMZjHzVNmqWsV0j6eb1hLihR6scvj6q/T0z5wkuUC3iIkK7VxL1 9a0yx/VNMrb9snjta+UbOn1NiodK8nEWty1sLF0KnBnd3aOQYMyAZiAjbCY3hBVX9d ZfimuV3Md6T7eESTF0p4Z04xJkR2nGj7mQ4ZB7aYhZV1poqsij9lVf/sJcwdcmBO4+ fzrCi3aOoqDyAC60DzYD9rG09yVUvvpPwqsztEnkTeZFvZ5J/iUqGiIy6dxxkAZikD KN51r5rTE+n2g== Message-ID: <07f1039c-cf9b-4b97-a044-9d5771ea54fb@kernel.org> Date: Wed, 13 May 2026 17:36:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/9] mm: introduce pgtable_has_pmd_leaves() To: Luiz Capitulino , linux-kernel@vger.kernel.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, ziy@nvidia.com, lance.yang@linux.dev 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, dave.hansen@linux.intel.com, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com References: <2a0bae00cdd2b6ef6b962610b523ebfc97806ba7.1777663129.git.luizcap@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: BB04CA000B X-Rspamd-Server: rspam06 X-Stat-Signature: fzrdoiuys19k6ytzskfbogts5f9bfxgh X-HE-Tag: 1778686605-601995 X-HE-Meta: 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 sW2OWdkE B5zQqgJywCqU5+MtzaLmcB+CNcgMJxKSyAwilrAy5DZiLumTSltrp+METVdKLJ9pdzmwu0eLAU8Qj5UxniSHHRG0xLYgbRs4ygh43vnCbnSCXAkhc5Kx9NMgEE27eSh8/YroaRXRq98WczGZWs12P73NjqjbgL04PuygMiQTOIf8hmw95Kp3+aTVBJfO0XACVs/fCX+SFnnPCubSKI1FOOQSV98iORUdWxb71vBNvYFW8alpFQ4e+IpA6SoWoOfvzpv7XbLHMhDr0oCyjKqr6vuJ3mh4E4s2YPf670DwomheJ/npI59cJsRFLjw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/1/26 21:18, Luiz Capitulino wrote: > Currently, we have two helpers that check for PMD-sized pages but have > different names and slightly different semantics: > > - has_transparent_hugepage(): the name suggests it checks if THP is > enabled, but when CONFIG_TRANSPARENT_HUGEPAGE=y and the architecture > implements this helper, it actually checks if the CPU supports > PMD-sized pages > > - thp_disabled_by_hw(): the name suggests it checks if THP is disabled > by the hardware, but it just returns a cached value acquired with > has_transparent_hugepage(). This helper is used in fast paths > > This commit introduces a new helper called pgtable_has_pmd_leaves() > which is intended to replace both has_transparent_hugepage() and > thp_disabled_by_hw(). pgtable_has_pmd_leaves() has very clear semantics: > it returns true if the CPU supports PMD-sized pages and false otherwise. > It always returns a cached value, so it can be used in fast paths. Oh, one more thing: what will be the semantics regarding CONFIG_TRANSPARENT_HUGEPAGE? I assume it will only return true if CONFIG_TRANSPARENT_HUGEPAGE is enabled, correct? That is, for example, relevant for patch #2. We could later change these semantics, but for now we should be very clear about what it means. -- Cheers, David