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Fri, 16 Jan 2026 07:32:00 +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 jQHIG3DpaWlfTAAAD6G6ig (envelope-from ); Fri, 16 Jan 2026 07:32:00 +0000 Message-ID: Date: Fri, 16 Jan 2026 08:32:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 08/20] slab: add optimized sheaf refill from partial list 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 References: <20260112-sheaves-for-all-v2-0-98225cfb50cf@suse.cz> <20260112-sheaves-for-all-v2-8-98225cfb50cf@suse.cz> <38de0039-e0ea-41c4-a293-400798390ea1@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-Stat-Signature: w9ho9b8kd5fiw6hxwch49hxtxdt95796 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 06036180005 X-Rspam-User: X-HE-Tag: 1768548723-437008 X-HE-Meta: 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 0oxHOssG fb/vlqiUIFFcLs4iRfA/NZexbbhDGUubFHQGV/urCPMtP6PDQQlCicNj7gyuCMg3vdBadKpdlR0ZT7aQOKiAJJ4k5PCcKdtGIucAxW4zuWpp8xnHjjC1fb8cYmlKsbZc68YGMAWjkcymh6opz9GH5btKehpA3XxJ36ikINYL6vF3ro/Y1rM9gQ2PdXplKz8IOUNYowVdP6y7h9fxKRNMEHE8XB6RH6oJ2HKq1YSorf5ED22fctwjRwLGWgV0+Fe7Lx2qWYpxyWFWSE1e9zFuT4NCvWogX3+o6L/gR 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 1/16/26 07:27, Hao Li wrote: > On Thu, Jan 15, 2026 at 03:25:59PM +0100, Vlastimil Babka wrote: >> On 1/12/26 16:17, Vlastimil Babka wrote: >> > At this point we have sheaves enabled for all caches, but their refill >> > is done via __kmem_cache_alloc_bulk() which relies on cpu (partial) >> > slabs - now a redundant caching layer that we are about to remove. >> > >> > The refill will thus be done from slabs on the node partial list. >> > Introduce new functions that can do that in an optimized way as it's >> > easier than modifying the __kmem_cache_alloc_bulk() call chain. >> > >> > Extend struct partial_context so it can return a list of slabs from the >> > partial list with the sum of free objects in them within the requested >> > min and max. >> > >> > Introduce get_partial_node_bulk() that removes the slabs from freelist >> > and returns them in the list. >> > >> > Introduce get_freelist_nofreeze() which grabs the freelist without >> > freezing the slab. >> > >> > Introduce alloc_from_new_slab() which can allocate multiple objects from >> > a newly allocated slab where we don't need to synchronize with freeing. >> > In some aspects it's similar to alloc_single_from_new_slab() but assumes >> > the cache is a non-debug one so it can avoid some actions. >> > >> > Introduce __refill_objects() that uses the functions above to fill an >> > array of objects. It has to handle the possibility that the slabs will >> > contain more objects that were requested, due to concurrent freeing of >> > objects to those slabs. When no more slabs on partial lists are >> > available, it will allocate new slabs. It is intended to be only used >> > in context where spinning is allowed, so add a WARN_ON_ONCE check there. >> > >> > Finally, switch refill_sheaf() to use __refill_objects(). Sheaves are >> > only refilled from contexts that allow spinning, or even blocking. >> > >> > Signed-off-by: Vlastimil Babka >> >> ... >> >> > +static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab, >> > + void **p, unsigned int count, bool allow_spin) >> > +{ >> > + unsigned int allocated = 0; >> > + struct kmem_cache_node *n; >> > + unsigned long flags; >> > + void *object; >> > + >> > + if (!allow_spin && (slab->objects - slab->inuse) > count) { >> > + >> > + n = get_node(s, slab_nid(slab)); >> > + >> > + if (!spin_trylock_irqsave(&n->list_lock, flags)) { >> > + /* Unlucky, discard newly allocated slab */ >> > + defer_deactivate_slab(slab, NULL); >> >> This actually does dec_slabs_node() only with slab->frozen which we don't set. > > Hi, I think I follow the intent, but I got a little tripped up here: patch 08 > (current patch) seems to assume "slab->frozen = 1" is already gone. That's true > after the whole series, but the removal only happens in patch 09. > > Would it make sense to avoid relying on that assumption when looking at patch 08 > in isolation? Hm I did think it's fine. alloc_from_new_slab() introduced here is only used from __refill_objects() and that one doesn't set slab->frozen = 1 on the new slab? Then patch 09 switches ___slab_alloc() to alloc_from_new_slab() and at the same time also stops setting slab->frozen = 1 so it should be also fine. And then 12/20 slab: remove defer_deactivate_slab() removes the frozen = 1 treatment as nobody uses it anymore. If there's some mistake in the above, please tell! Thanks.