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Thu, 01 May 2025 16:43:28 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:7255:67a0:34ee:5b40]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-30a3482a35csm4245166a91.44.2025.05.01.16.43.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 May 2025 16:43:27 -0700 (PDT) Date: Fri, 2 May 2025 08:43:22 +0900 From: Sergey Senozhatsky To: Vitaly Wool Cc: Yosry Ahmed , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Nhat Pham , Shakeel Butt , Johannes Weiner , Igor Belousov , Minchan Kim , Sergey Senozhatsky Subject: Re: [PATCH v4] mm: add zblock allocator Message-ID: References: <20250412154207.2152667-1-vitaly.wool@konsulko.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: bhmz6gm8o5t8i53yntny8qeoi5nyqccd X-Rspamd-Queue-Id: AEC85C0002 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1746143009-617678 X-HE-Meta: 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 rFrEXDGS 6AK6q1T+jobjKHLld49FoPFj88oduTy+5yDa1EDHUUM6iKOZJ0lsUGxcf4xFnoM7XqyenQvETejUcqbWYAhFHkR7d9ZIlRxKMmdHBmTLTxb7cwypmlYvdGWS+LL5yvuOeVs23m/OCyXmZqpfvOdE9g4Idt2s3J+z9TSIxqdypSL2au8iI6YhM3j6Lh3DrzwGLh1SoHT9X8TNgMZjMd+JimlpDTaRjlTNUJbPrVJVVvEvs4sj2X30GA11VjPFZOd/11wqruK847V9GiTWn3WQVFMaoUimX0EPCNau4rBI5k/E303TfR77Y/hEPPe6R2z+OHRIdrDLxzTsU67/D4xj72D1+yELdjGMmfLkB8HhUFwInvyo= 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 (25/05/01 14:41), Vitaly Wool wrote: [..] > Bottom line, ending up with a lot of blocks each containing a single object > is not a real life scenario. Why not? What if the data patterns do not favor compressible objects? E.g. what if the distribution of compressed objects looks like this (a real zsmalloc stats): size-class objs-allocated --------------------------- ... 1904 3315 1920 3468 1936 3515 2048 25816 2144 22363 2160 3230 2176 3075 2192 2990 2224 5665 2272 8118 2304 5040 2336 4529 2384 6132 2400 1768 2448 4825 2512 5135 2560 2944 2592 1562 2624 1512 2720 3813 2832 3315 2864 820 ... Notice tenth of thousands of 2048-2144 bytes objects. zsmalloc size classes are fundamentally independent of each other and, hence, of the compressed objects distribution: the lack of objects, or even "the absence of" for that matter, in size-class 256 does not change a thing for size-class 2048. This is a very important property.