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Thu, 29 Jan 2026 10:39:05 +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 2t7NAck4e2lNcQAAD6G6ig (envelope-from ); Thu, 29 Jan 2026 10:39:05 +0000 Message-ID: <00e257f0-d80d-408e-963c-7962a1cef9d8@suse.cz> Date: Thu, 29 Jan 2026 11:39:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slub: avoid list_lock contention from __refill_objects_any() Content-Language: en-US To: Harry Yoo , Hao Li Cc: Mateusz Guzik , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot References: <20260129-b4-refill_any_trylock-v1-1-de7420b25840@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-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D99461C000C X-Stat-Signature: siyr31z8g767t9otk93cigxmyeite75f X-HE-Tag: 1769683146-68017 X-HE-Meta: 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 UIN4RJYW 05qDcV9Djdx4OBVIWUf4SZHDHEb+TIUmiIjOca4HNZxsHV66xGjAz5I22NkzSRB1t6oqz6sX6M7dUDk0En7tk6rXjROOEokBHgxDtX6B48fb/IXdKAHGl9C7G6XiBkM9B2uF+/vLXil1vxE60KvKi1b6fHEYwRZS5f+74umxzGgm/oCYQBAYua6d1D9xntWVfCeBAdkBMQdMUoYD49P3MlWCOQXt0VHwYATPX8bSMjtikFvLJDXYqf8cNDxcS3IhSPukjOTiRBpAEYbG5wJZzJltOLSPaybvgzHWcUFrKNAvbHb96aPv+viXvcJK3e9Bs4FWwoKgZs4gvexmi6xYJKkMhSh8dpqzVWE09Mh6aNjRQ2YAat5nYxPkFlee6BJbmPRZI 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 1/29/26 10:30, Harry Yoo wrote: > On Thu, Jan 29, 2026 at 05:21:21PM +0800, Hao Li wrote: >> On Thu, Jan 29, 2026 at 10:07:57AM +0100, Vlastimil Babka wrote: >> > Kernel test robot has reported a regression in the patch "slab: refill >> > sheaves from all nodes". When taken in isolation like this, there is >> > indeed a tradeoff - we prefer to use remote objects prior to allocating >> > new local slabs. It is replicating a behavior that existed before >> > sheaves for replenishing cpu (partial) slabs - now called >> > get_from_any_partial() to allocate a single object. >> > >> > So the possibility of allocating remote objects is intended even if >> > remote accesses are then slower. But the profiles in the report also >> > suggested a contention on the list_lock spinlock. And that's something >> > we can try to avoid without much tradeoff - if someone else has the >> > spin_lock, it's more likely they are allocating from the node than >> > freeing to it, so we can skip it even if it means allocating a new local >> > slab - contributing to that lock's contention isn't worth it. It should >> > not result in partial slabs accumulating on the remote node. >> > >> > Thus add an allow_spin parameter to __refill_objects_node() and >> > get_partial_node_bulk() to make the attempts from __refill_objects_any() >> > use only a trylock. >> > >> > Reported-by: kernel test robot >> > Link: https://lore.kernel.org/oe-lkp/202601132136.77efd6d7-lkp@intel.com >> > Signed-off-by: Vlastimil Babka >> >> In my testing, this patch improved performance by: >> >> will-it-scale.64.processes +14.2% >> will-it-scale.128.processes +9.6% >> will-it-scale.192.processes +10.8% >> will-it-scale.per_process_ops +11.6% >> >> Tested-by: Hao Li > > I wonder if using spin_is_contended() or spin_is_locked() > would be better than trylock by avoiding an atomic operation? I checked and found that spin_trylock() itself implements a non-atomic check before the atomic. So adding a spin_is_locked() would only help the caller bail out a bit faster, but this is not a fastpath. It wouldn't help the cache coherency traffic, AFAIU.