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Mon, 12 Dec 2022 05:11:15 -0800 (PST) Received: from fedora ([216.211.255.155]) by smtp.gmail.com with ESMTPSA id f9-20020a05620a280900b006ff8a122a1asm3626860qkp.78.2022.12.12.05.11.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 05:11:13 -0800 (PST) Date: Mon, 12 Dec 2022 05:11:11 -0800 From: Dennis Zhou To: Vlastimil Babka Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Baoquan He , Christoph Lameter , David Rientjes , Joonsoo Kim , Pekka Enberg , Roman Gushchin , Andrew Morton , Linus Torvalds , Matthew Wilcox , patches@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/12] mm, slub: remove percpu slabs with CONFIG_SLUB_TINY Message-ID: References: <20221121171202.22080-1-vbabka@suse.cz> <20221121171202.22080-11-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: jn311fstihquaobds8wd8hony5k44jh5 X-Rspam-User: X-Rspamd-Queue-Id: 72C7F4001A X-Rspamd-Server: rspam06 X-HE-Tag: 1670850676-987213 X-HE-Meta: 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 n+giA7wv 9if+V8E6no289p3Tz+3A/IzgXzpj/ziutPl3o/m/j1izeJm2Ko4VOZFOScDnJ35Zrg82aBEmEjkTRvYwTpAkq4H0ifTQ/icXim3ZlI/H9G5J3xGBVc2+5OXSDG0DrCRuul8qmStSS8fwQbXuTKklelu1soPEaubjypTQ4V57j/irh9++GwpEHlwx5/MvoJ5pJHTbdOX0+rLq7OI3l0KFf+67N9MaFtXYnN+2ak4AO4JYHJayAdqvCPfYjZq509WXmmqxDzI8XdNOXmlSGi/B15ydoRUNegdWvtPh/iD/mMFdUVYiB6BThcZ2DuSK6fRaMuRWTdQ0tU+xTZNE= 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: Hello, On Mon, Dec 12, 2022 at 11:54:28AM +0100, Vlastimil Babka wrote: > On 11/27/22 12:05, Hyeonggon Yoo wrote: > > On Mon, Nov 21, 2022 at 06:12:00PM +0100, Vlastimil Babka wrote: > >> SLUB gets most of its scalability by percpu slabs. However for > >> CONFIG_SLUB_TINY the goal is minimal memory overhead, not scalability. > >> Thus, #ifdef out the whole kmem_cache_cpu percpu structure and > >> associated code. Additionally to the slab page savings, this reduces > >> percpu allocator usage, and code size. > > > > [+Cc Dennis] > > +To: Baoquan also. > > > Wondering if we can reduce (or zero) early reservation of percpu area > > when #if !defined(CONFIG_SLUB) || defined(CONFIG_SLUB_TINY)? > > Good point. I've sent a PR as it was [1], but (if merged) we can still > improve that during RC series, if it means more memory saved thanks to less > percpu usage with CONFIG_SLUB_TINY. > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/tag/?h=slab-for-6.2-rc1 The early reservation area not used at boot is then used to serve normal percpu allocations. Percpu allocates additional chunks based on a free page float count and is backed page by page, not all at once. I get slabs is the main motivator of early reservation, but if there are other users of percpu, then shrinking the early reservation area is a bit moot. Thanks, Dennis > > >> This change builds on recent commit c7323a5ad078 ("mm/slub: restrict > >> sysfs validation to debug caches and make it safe"), as caches with > >> enabled debugging also avoid percpu slabs and all allocations and > >> freeing ends up working with the partial list. With a bit more > >> refactoring by the preceding patches, use the same code paths with > >> CONFIG_SLUB_TINY. > >> > >> Signed-off-by: Vlastimil Babka > > >