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Mon, 19 Jan 2026 10:23:05 +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 jRWXAAkGbmndCgAAD6G6ig (envelope-from ); Mon, 19 Jan 2026 10:23:05 +0000 Message-ID: <008029ff-3fd8-49cf-8aa7-71b98dc15be9@suse.cz> Date: Mon, 19 Jan 2026 11:23:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 07/21] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree_nolock() Content-Language: en-US From: Vlastimil Babka To: Harry Yoo Cc: Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin , Hao Li , 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: <20260116-sheaves-for-all-v3-0-5595cb000772@suse.cz> <20260116-sheaves-for-all-v3-7-5595cb000772@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EE811140003 X-Stat-Signature: 4i41qnh71ewcdnxatznyxfomk484541a X-HE-Tag: 1768818186-171233 X-HE-Meta: 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 ECz6H8op qf2hk5KrPsifGGf8= 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 1/19/26 11:09, Vlastimil Babka wrote: > On 1/19/26 05:31, Harry Yoo wrote: >> On Fri, Jan 16, 2026 at 03:40:27PM +0100, Vlastimil Babka wrote: >>> Before we enable percpu sheaves for kmalloc caches, we need to make sure >>> kmalloc_nolock() and kfree_nolock() will continue working properly and >>> not spin when not allowed to. >>> >>> Percpu sheaves themselves use local_trylock() so they are already >>> compatible. We just need to be careful with the barn->lock spin_lock. >>> Pass a new allow_spin parameter where necessary to use >>> spin_trylock_irqsave(). >>> >>> In kmalloc_nolock_noprof() we can now attempt alloc_from_pcs() safely, >>> for now it will always fail until we enable sheaves for kmalloc caches >>> next. Similarly in kfree_nolock() we can attempt free_to_pcs(). >>> >>> Signed-off-by: Vlastimil Babka >>> --- >> >> Looks good to me, >> Reviewed-by: Harry Yoo > > Thanks. > >> >> with a nit below. >> >>> mm/slub.c | 79 ++++++++++++++++++++++++++++++++++++++++++++------------------- >>> 1 file changed, 56 insertions(+), 23 deletions(-) >>> >>> diff --git a/mm/slub.c b/mm/slub.c >>> index 706cb6398f05..b385247c219f 100644 >>> --- a/mm/slub.c >>> +++ b/mm/slub.c >>> @@ -6703,7 +6735,7 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object, >>> >>> if (likely(!IS_ENABLED(CONFIG_NUMA) || slab_nid(slab) == numa_mem_id()) >>> && likely(!slab_test_pfmemalloc(slab))) { >>> - if (likely(free_to_pcs(s, object))) >>> + if (likely(free_to_pcs(s, object, true))) >>> return; >>> } >>> >>> @@ -6964,7 +6996,8 @@ void kfree_nolock(const void *object) >>> * since kasan quarantine takes locks and not supported from NMI. >>> */ >>> kasan_slab_free(s, x, false, false, /* skip quarantine */true); >>> - do_slab_free(s, slab, x, x, 0, _RET_IP_); >>> + if (!free_to_pcs(s, x, false)) >>> + do_slab_free(s, slab, x, x, 0, _RET_IP_); >>> } >> >> nit: Maybe it's not that common but should we bypass sheaves if >> it's from remote NUMA node just like slab_free()? > > Right, will do. However that means sheaves will help less with the defer_free() avoidance here. It becomes more obvious after "slab: remove the do_slab_free() fastpath". All remote object frees will be deferred. Guess we can revisit later if we see there are too many and have no better solution... >>> EXPORT_SYMBOL_GPL(kfree_nolock); >>> >>> @@ -7516,7 +7549,7 @@ int kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, size_t size, >>> size--; >>> } >>> >>> - i = alloc_from_pcs_bulk(s, size, p); >>> + i = alloc_from_pcs_bulk(s, flags, size, p); >>> >>> if (i < size) { > /* >>> >> >