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Mon, 15 Sep 2025 07:21:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 4SWdIGy+x2gAUQAAD6G6ig (envelope-from ); Mon, 15 Sep 2025 07:21:16 +0000 Message-ID: <02568985-b6c0-45cd-924b-f86f7975c119@suse.cz> Date: Mon, 15 Sep 2025 09:21:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 01/14] slab: add opt-in caching layer of percpu sheaves To: Hillf Danton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250915001139.7101-1-hdanton@sina.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20250915001139.7101-1-hdanton@sina.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6A0D4180002 X-Rspamd-Server: rspam05 X-Stat-Signature: 1td1ewz9y3sj8o3gpkg9afh9g1bnumx5 X-Rspam-User: X-HE-Tag: 1757920878-740563 X-HE-Meta: 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 l48IUPLA 600+Pj0VpFFVMVDt81eytceGwuZ/3IU2nyB8VgJyuUkPoFVRbhDfEQSHv8K9H7oNT6571IzMx7bS8Jv2qH6tO9ZSypCBe3zbqPBqkByNdW60jeemb4Rl4uwkGnnuG7eWQtJYhwXNyGL/+wWMkKsOun4mMg95uKhw0BFbKA8XJbFdCZQdB4jV+rHejpM4WBlfe9+Nw4lDpVidAR3Hk+GdWPUYMUArk1JivfYTX9E7qOX8qa6YyWNc4uwhRyA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/15/25 02:11, Hillf Danton wrote: > On Sun, 14 Sep 2025 22:24:19 +0200 Vlastimil Babka wrote: >>On 9/14/25 04:22, Hillf Danton wrote: >>> On Wed, 23 Jul 2025 15:34:34 +0200 Vlastimil Babka wrote: >>> Migration is not disabled. >> >> Can you elaborate how it's not? There's a comment above the function saying >> "Called from CPU work handler with migration disabled." and we have relied >> on this before sheaves. queue_work_on() says it will run on the specific >> cpu. AFAIK the workqueue workers are bound which is effectively disabled >> migration (we hold the cpu hotplug lock). >> > CPU affinity and migration_disable() are two different things regardless of > queue_work_on(), no? Well as long as it means the execution of pcs_flush_all() won't change the cpu it's running on in the middle of the operation, it's the same. > I think you are right in accident rather than by design in this case. I don't see a mistake in the design, there are many queue_work_on() users relying on this property. It's only the comment wording where "make sure migration is disabled" makes you expect there to be a migrate_disable() somewhere? But why if it's not necessary?