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Wed, 14 Jan 2026 14:05:35 +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 DBFZCK+iZ2mlNAAAD6G6ig (envelope-from ); Wed, 14 Jan 2026 14:05:35 +0000 Message-ID: Date: Wed, 14 Jan 2026 15:05:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 06/20] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree_nolock() Content-Language: en-US From: Vlastimil Babka To: Alexei Starovoitov , Sebastian Andrzej Siewior Cc: Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin , Hao Li , Andrew Morton , Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , Alexei Starovoitov , linux-mm , LKML , linux-rt-devel@lists.linux.dev, bpf , kasan-dev References: <20260112-sheaves-for-all-v2-0-98225cfb50cf@suse.cz> <20260112-sheaves-for-all-v2-6-98225cfb50cf@suse.cz> <20260113183604.ykHFYvV2@linutronix.de> <596a5461-eb50-40e5-88ca-d5dbe1fc6a67@suse.cz> 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: <596a5461-eb50-40e5-88ca-d5dbe1fc6a67@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 1BC8E40010 X-Stat-Signature: 4af5757u5iz8bbiy9kzxp8o8hpogbruo X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768399536-942156 X-HE-Meta: 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 A7XiV6GF qtPyqph6misuWLugFkHtm7j+Y+1cLuPfkvPMDOYWnkzrLEQnifUYi9TtTin71gZQFXdQYEWVqIONHKZWKsXxiSF06XgVTl5Kcrea01WLFmzLs63g9WzfBJzgXWq1ClJupv5g0kIBgEZiHKLlSCMnQXS11n/ykbNU2RVwBLpqnIggNZKpl7iuxz3+nsltWYfusIJHlX5oFhdqjIzyHoko/aUAnNGkydQ8izLtOkmIh/lWKTVapqjCdY/LDEjc9ClsbvkBX4u41F7d6Vl7nBfuOwI+TVjIHb0HU/ffh7uk3KBE6MdRkMOlmiwxNJlhLl3vkvgMkwsvla6gBYXxBi2HKVmGu8fMAbSJUaezaf43XD3FatvzMyhaIjI66nEMYQfqWfn1yg+13qhSLDJEljtVabNCNGGKUh2cCTnTYC3QF1BZz125VURgDcx2ep0apD/ID2rMOMHdVfwFsR7/YAwRIT8fc6Uyexz6EaUYn 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 1/14/26 14:57, Vlastimil Babka wrote: > On 1/14/26 00:26, Alexei Starovoitov wrote: >> On Tue, Jan 13, 2026 at 10:36 AM Sebastian Andrzej Siewior >> wrote: >>> >>> On 2026-01-12 16:17:00 [+0100], Vlastimil Babka wrote: >>> > --- a/mm/slub.c >>> > +++ b/mm/slub.c >>> > @@ -5727,6 +5742,12 @@ void *kmalloc_nolock_noprof(size_t size, gfp_t gfp_flags, int node) >>> > */ >>> > return NULL; >>> > >>> > + ret = alloc_from_pcs(s, alloc_gfp, node); >>> > + if (ret) >>> > + goto success; >>> >>> I'm sorry if I am slow but this actually should actually allow >>> kmalloc_nolock() allocations on PREEMPT_RT from atomic context. I am >>> mentioning this because of the patch which removes the nmi+hardirq >>> condtion (https://lore.kernel.org/all/20260113150639.48407-1-swarajgaikwad1925@gmail.com) >> >> Right. With sheaves kmalloc_nolock() on RT will be more reliable. > > Yes IIRC Hao Li pointed that out before. We'll be able to remove that > !preemptible() check that we area about to add by the patch above. > > But I'm not sure we can remove (or "not put back") the "in_nmi() || > in_hardirq()" too, because as you said it was added with different reasoning > initially? Ah right, it was "copied" from alloc_frozen_pages_nolock_noprof() where it's explained more, and AFAICS will be still applicable with sheaves. We should add a comment to kmalloc_nolock() referring to the alloc_frozen_pages_nolock_noprof() comment...