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Wed, 4 Feb 2026 18:02:27 +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 RZfcCbOJg2nwKQAAD6G6ig (envelope-from ); Wed, 04 Feb 2026 18:02:27 +0000 Message-ID: <665ff739-73d8-4996-95e0-f09c3e5b6552@suse.cz> Date: Wed, 4 Feb 2026 19:02:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 00/22] slab: replace cpu (partial) slabs with sheaves Content-Language: en-US To: Hao Li Cc: Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin , Andrew Morton , Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , Sebastian Andrzej Siewior , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com, kernel test robot , stable@vger.kernel.org, "Paul E. McKenney" References: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> <390d6318-08f3-403b-bf96-4675a0d1fe98@suse.cz> 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-Server: rspam11 X-Stat-Signature: tssuc9podw77ky5kb1wbtpum6ddqgf9x X-Rspam-User: X-Rspamd-Queue-Id: 01363140012 X-HE-Tag: 1770228148-721874 X-HE-Meta: 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 MY6+3BmV i+6YFd37Fevx/EVruUwTu539f7scKd70dkhbNVXL+NgDJwlPFjt5xF6kRWpA1W8OSC62DmnJS8iE3IzGEQdgkgJpWyGNwnhNhBfN45nJUDsruEPWC7mgamhFUR7WvtXZsyy6mWz5h1zPuGAt7kao6Z6w33lBYViThgpR+YOby2YB/O8hXmizHSkXu47vXbum0bBGCb0Lr1H6TSYjrCj26+96UkNatzOd1qlb9GNcoaSQ/3r+8FK+l8XF6EqCY7cOUx9K4v3cbFfuhuiFiivY87udvs4fjOkYlkhrG 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 1/30/26 05:50, Hao Li wrote: > On Thu, Jan 29, 2026 at 04:28:01PM +0100, Vlastimil Babka wrote: >> >> So previously those would become kind of double >> cached by both sheaves and cpu (partial) slabs (and thus hopefully benefited >> more than they should) since sheaves introduction in 6.18, and now they are >> not double cached anymore? >> > > I've conducted new tests, and here are the details of three scenarios: > > 1. Checked out commit 9d4e6ab865c4, which represents the state before the > introduction of the sheaves mechanism. > 2. Tested with 6.19-rc5, which includes sheaves but does not yet apply the > "sheaves for all" patchset. > 3. Applied the "sheaves for all" patchset and also included the "avoid > list_lock contention" patch. > > > Results: > > For scenario 2 (with sheaves but without "sheaves for all"), there is a > noticeable performance improvement compared to scenario 1: > > will-it-scale.128.processes +34.3% > will-it-scale.192.processes +35.4% > will-it-scale.64.processes +31.5% > will-it-scale.per_process_ops +33.7% > > For scenario 3 (after applying "sheaves for all"), performance slightly > regressed compared to scenario 1: > > will-it-scale.128.processes -1.3% > will-it-scale.192.processes -4.2% > will-it-scale.64.processes -1.2% > will-it-scale.per_process_ops -2.1% > > Analysis: > > So when the sheaf size for maple nodes is set to 32 by default, the performance > of fully adopting the sheaves mechanism roughly matches the performance of the > previous approach that relied solely on the percpu slab partial list. > > The performance regression observed with the "sheaves for all" patchset can > actually be explained as follows: moving from scenario 1 to scenario 2 > introduces an additional cache layer, which boosts performance temporarily. > When moving from scenario 2 to scenario 3, this additional cache layer is > removed, then performance reverted to its original level. > > So I think the performance of the percpu partial list and the sheaves mechanism > is roughly the same, which is consistent with our expectations. Thanks!