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b=bSW/zCu2pqN1wyQJbp3qqbY97+FtE6YoCwLIy7QWHBOdR2OZssMnQJaHk84GfbWW1 At1hCpU4kt/XExzHY8E0cBRDNl7dhDPO6qhz5S6Ms7OnzeU17RRoh2dfRIoyJW/4YF 0NDu4bpq07VS85t1qupING3Z/E5e6UvDlPbRxSHIJnVLnY9rOaHMVL0frWeBdMK5tU spEURThLmhVIwXZH+Hopsk3UXu05Pd5xlehD7gA5VcXRKQXhm9U4BOe6rZuhSVrzu2 mgKRgHY4j5sGAtT2fpEg4iw8NN9Med1DIC7q4eXUL+1ug4um38g2r53s8geo49YlK8 CiXmBChnkhmKw== Date: Tue, 4 Aug 2026 18:32:47 +0100 From: "Lorenzo Stoakes (ARM)" To: Linus Torvalds Cc: "Christoph Lameter (Ampere)" , "David Hildenbrand (Arm)" , Mark Rutland , Yang Shi , Ryan Roberts , dennis@kernel.org, tj@kernel.org, urezki@gmail.com, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jason Gunthorpe Subject: Re: [RFC v2 PATCH 0/16] Optimize this_cpu_*() ops for non-x86 (ARM64 for this series) Message-ID: References: <0344c559-1959-4531-9265-d5a5180eb7cd@arm.com> <25d1e09b-53e4-7cd5-87db-b58437e4e690@gentwo.org> <4887267b-dc26-4c33-96ca-8dff054a0d1f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B87E940011 X-Stat-Signature: py449db3aj84xwu5o3x6wbij3sbks5pr X-Rspam-User: X-HE-Tag: 1785864787-732335 X-HE-Meta: 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 c5lK0Tx3 7TwO0HluPyTxCxDO6CzJgSKJ3T/Ql50cZrkEYGCktXu3sDXAY5wAHTMfUE0nNiAwQ1FvDNOqdqU5vgPJIKzWilVxbiiYODQtxW0biaPBPoYuXMM/uBTbiojVD2THmp0/nQXvq5WEfDbdUrwhwqq+KrvqHBkTDEIVtS63Lz9dtSRAT5Y41FW1aVZZueahurKVS9JpQVXdmxj+NRBKA/MFD/NZTWfew+voMVvZuzPWicSNCEE3Yw89F13aMCJqTERewjsl1Rx6TGBMpJWvsXtTLk+vcf7XWmDrLYtY0n+eZg0xrSTs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 04, 2026 at 10:01:45AM -0700, Linus Torvalds wrote: > So I'm just trying to clarify my stance - I don't hate percpu TLB > contents per se. I hate the notion of codifying them. I do worry that changing per-CPU data structures to support this is exactly codifying this (and will encourage other arches to follow suit). And I really don't think there's any way to implement this without fundamentally changing core mm or assumptions that core mm can make. -- Cheers, Lorenzo