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Tue, 16 Sep 2025 10:21:25 +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 4DiWHCU6yWhDTAAAD6G6ig (envelope-from ); Tue, 16 Sep 2025 10:21:25 +0000 Message-ID: Date: Tue, 16 Sep 2025 12:21:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH slab] slab: Clarify comments regarding pfmemalloc and NUMA preferences Content-Language: en-US To: Alexei Starovoitov , bpf@vger.kernel.org, linux-mm@kvack.org Cc: harry.yoo@oracle.com, shakeel.butt@linux.dev, mhocko@suse.com, bigeasy@linutronix.de, andrii@kernel.org, memxor@gmail.com, akpm@linux-foundation.org, peterz@infradead.org, rostedt@goodmis.org, hannes@cmpxchg.org References: <20250916014609.47273-1-alexei.starovoitov@gmail.com> 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: <20250916014609.47273-1-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: g1swgiaaymqxasa65fwak73shsa4jy3d X-Rspamd-Queue-Id: 5389140003 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1758018087-270580 X-HE-Meta: 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 C0UEzY94 XOeIeYgqIdmI0cUNF/bo/Mn/s3V/HuBxRHkA3xVoMC51Ucw2EUDjruwl25yvFDaiO0Jp4OQz4swJguV23np8bn9afKQYAXgYc6p3e055MgJufUW4AGeWERRm6aRorVOd6YY7YsGNhUtHCEMZ3ke9Yn7VqUKYi5e3LghuLUTnX4IDYysUFmOGY/sb5PDzfmfuVrgjQARBBWdh2MQCeXzzaADoeXv/c47OfJD0kt8sW3K14RWep6GBwpglaGcVYZVpDNE5UC6pgCPRiHUdTDxL1ZAfcVCO2JpsoTe5EZGPLGn64Gtk8zxT9baoW334NJid3bpqRxDww/m52ZLHV05xEsn3th42oSNhFCLmqk6Lt6nRcyBU4B4nwmxYPGYURQquEgRq+ 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 9/16/25 03:46, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > Clarify comments regarding pfmemalloc and NUMA preferences > when ___slab_alloc() operating in !allow_spin mode. > > Signed-off-by: Alexei Starovoitov Folding that into "slab: Introduce kmalloc_nolock() and kfree_nolock()." in slab/for-next, thanks. > --- > mm/slub.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 83983de948f3..c995f3bec69d 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -4456,9 +4456,17 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > /* > * same as above but node_match() being false already > * implies node != NUMA_NO_NODE. > - * Reentrant slub cannot take locks necessary to > - * deactivate_slab, hence ignore node preference. > - * kmalloc_nolock() doesn't allow __GFP_THISNODE. > + * > + * We don't strictly honor pfmemalloc and NUMA preferences > + * when !allow_spin because: > + * > + * 1. Most kmalloc() users allocate objects on the local node, > + * so kmalloc_nolock() tries not to interfere with them by > + * deactivating the cpu slab. > + * > + * 2. Deactivating due to NUMA or pfmemalloc mismatch may cause > + * unnecessary slab allocations even when n->partial list > + * is not empty. > */ > if (!node_isset(node, slab_nodes) || > !allow_spin) { > @@ -4547,11 +4555,6 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > slab = slub_percpu_partial(c); > slub_set_percpu_partial(c, slab); > > - /* > - * Reentrant slub cannot take locks necessary for > - * __put_partials(), hence ignore node preference. > - * kmalloc_nolock() doesn't allow __GFP_THISNODE. > - */ > if (likely(node_match(slab, node) && > pfmemalloc_match(slab, gfpflags)) || > !allow_spin) {