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[34.64.229.252]) by smtp.gmail.com with ESMTPSA id t24sm2308860pgn.78.2021.09.29.03.50.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Sep 2021 03:51:01 -0700 (PDT) Date: Wed, 29 Sep 2021 10:50:56 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Vlastimil Babka Cc: linux-mm@kvack.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [QUESTION] is SLAB considered legacy and deprecated? Message-ID: <20210929105056.GA2575@linux.asia-northeast3-a.c.our-ratio-313919.internal> References: <20210927090347.GA2533@linux.asia-northeast3-a.c.our-ratio-313919.internal> <8aa15f4b-71de-5283-5ebc-d8d1a323473d@suse.cz> <20210928111231.GA2596@linux.asia-northeast3-a.c.our-ratio-313919.internal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210928111231.GA2596@linux.asia-northeast3-a.c.our-ratio-313919.internal> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C2B52B0000AF X-Stat-Signature: grmqc9hngip3xsfe3g3yopu9ude1gp4r Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="RyMsCYE/"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf19.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.214.173 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com X-HE-Tag: 1632912662-429971 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: On Tue, Sep 28, 2021 at 11:12:36AM +0000, Hyeonggon Yoo wrote: > SLAB uses much memory than slab, not slab, slub. > when there are *lots* of NUMA nodes. > because kmem_cache_node exist per node and it keeps alien cache > (used for caching freeing object from remote node), > so it keeps MAX_NUMANODES ^ 2 of array_cache per slab. not "per slab". it is per cache (kmem_cache). it was my mistake. but that is still too much for systems with high number of numa nodes. batching freeing object from remote node is needed, but slab uses too much memory for that. for each node, it allocates alien cache for every other nodes. so it's using MAX_NUMNODES ^ 2 alien_cache. > that is why I said SLAB uses much memory than SLUB.