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Sat, 13 Sep 2025 20:32:54 +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 zXW8FvbUxWiYYQAAD6G6ig (envelope-from ); Sat, 13 Sep 2025 20:32:54 +0000 Message-ID: Date: Sat, 13 Sep 2025 22:32:54 +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: Mateusz Guzik Cc: Suren Baghdasaryan , "Liam R. Howlett" , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org References: <20250723-slub-percpu-caches-v5-0-b792cd830f5d@suse.cz> <20250723-slub-percpu-caches-v5-1-b792cd830f5d@suse.cz> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 24675180002 X-Stat-Signature: z13xntcza6wwne7xiix46t6tdxyx69gd X-Rspam-User: X-HE-Tag: 1757795576-678814 X-HE-Meta: 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 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 9/13/25 16:35, Mateusz Guzik wrote: > On Wed, Jul 23, 2025 at 03:34:34PM +0200, Vlastimil Babka wrote: >> The sheaves do not distinguish NUMA locality of the cached objects. > > While currently sheaves are opt-in, to my understanding the plan is to > make this the default. > > I would argue a hard requirement for a general purpose allocator in this > day and age is to provide node-local memory by default. Notably if you > have a workload which was careful to bind itself to one node, it should > not receive memory backed by other nodes unless there is no other > option. AFAIU this is satisifed with the stock allocator on the grounds > of running on a given domain, without having to explicitly demand memory > from it for everyting. > > I expect the lack of NUMA-awareness to result in increased accumulation > of "mismatched" memory as uptime goes up, violating the above. Yeah this is addressed in later patch in the series "mm, slub: skip percpu sheaves for remote object freeing" and then "mm, slab: allow NUMA restricted allocations to use percpu sheaves" further improves it. I should update commit log in this patch too. > I admit though I don't have a good solution as to how to handle the > "bad" frees. Someone (I think you?) stated that one of the previous > allocators was just freeing to per-domain lists or arrays and that was > causing trouble -- perhaps this would work if it came with small limits > in place for how big these can get? Yes, the alien arrays of SLAB, with their dreaded periodical flushing. To avoid that the later patch simply skips the percpu sheaf. Only about 5% of frees seem to be remote, so 95% will still benefit.