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Thu, 12 Feb 2026 14:28:18 +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 03qkLYLjjWmKOwAAD6G6ig (envelope-from ); Thu, 12 Feb 2026 14:28:18 +0000 Message-ID: <4808fda0-c663-4a52-a6ee-6c47497793c4@suse.cz> Date: Thu, 12 Feb 2026 15:28:18 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/7] k[v]free_rcu() improvements Content-Language: en-US To: Harry Yoo , Andrew Morton Cc: Christoph Lameter , David Rientjes , Roman Gushchin , Johannes Weiner , Shakeel Butt , Michal Hocko , Hao Li , Alexei Starovoitov , Puranjay Mohan , Andrii Nakryiko , Amery Hung , Catalin Marinas , "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Dave Chinner , Qi Zheng , Muchun Song , rcu@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org References: <20260206093410.160622-1-harry.yoo@oracle.com> 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: <20260206093410.160622-1-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 509901C000A X-Stat-Signature: 1eco3x63uinwgmipzpzepx3jqdaahmgf X-Rspam-User: X-HE-Tag: 1770906501-652548 X-HE-Meta: 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 f+vf/Hd2 G8qnRj7nfOBQQ7Jve3OZ9QjPX2rj8+QQok9gue1yHHK6cloL5aaZJoFAPotN/u5ZIXjtogiZvKhSeST+5yEpXQb9kXw== 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 2/6/26 10:34, Harry Yoo wrote: > These are a few improvements for k[v]free_rcu() API, which were suggested > by Alexei Starovoitov. > > [ To kmemleak folks: I'm going to teach delete_object_full() and > paint_ptr() to ignore cases when the object does not exist. > Could you please let me know if the way it's done in patch 3 > looks good? Only part 2 is relevant to you. ] > > Although I've put some effort into providing a decent quality > implementation, I'd like you to consider this as a proof-of-concept > and let's discuss how best we could tackle those problems: > > 1) Allow an 8-byte field to be used as an alternative to > struct rcu_head (16-byte) for 2-argument kvfree_rcu() > 2) kmalloc_nolock() -> kfree[_rcu]() support > 3) Add kfree_rcu_nolock() for NMI context Since you went bravely into this area, I'd like to suggest some more :) - teach CONFIG_KVFREE_RCU_BATCHED to handle kfree_rcu sheaves after they fill, instead of the standard call_rcu() handling - make kvfree_call_rcu() -> kfree_rcu_sheaf() compatible with PREEMPT_RT Thanks, Vlastimil