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[124.209.188.1]) by smtp.gmail.com with ESMTPSA id m20-20020aa78a14000000b005a77b030b5csm233041pfa.88.2023.02.06.17.47.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Feb 2023 17:47:32 -0800 (PST) Date: Tue, 7 Feb 2023 10:47:28 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Sergey Senozhatsky , Minchan Kim , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/2] zsmalloc: fine-grained inuse ratio based fullness grouping Message-ID: References: <20230206092559.2722946-1-senozhatsky@chromium.org> <20230206092559.2722946-3-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 562C1C0007 X-Stat-Signature: zttkuuh8p7gseschzxptaswjuhpiyxa4 X-HE-Tag: 1675734454-299494 X-HE-Meta: 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 GoFnb8W9 Ad9PWF84+jUQEL6owm0M93tjD7BrvK00XZ1N3TUJjyyBmW9hy4zQjLmcivvoT2w9IwMonrnTVORyu7pjnffdkMQ6o7MMfzpuc+kh1SlAirCubOVLBBZIAF7zHjt5FCrHUg0DifrFzAnTRDBb2nfLmuD7/j2NeM61BPs60fjSM+zgqrtr3boq0Kp1TLpQWsjwiUfxpFN/X3HyyUlfSsE5ZiPRk29Q9DxC8V6FV50MLdq49wBdkw7lrbZXMy9PQyNxiHP7KtDm023w7yS6oPnR+z0s9O7oWz2a2Tia+g4vAnff5XzCnfyjXipf/o7gh+v9AEU+V8K+mEDRKJo4GENR67uQXHtgRzgiLDTL02GxZenBtu8sGyCjTANCdRA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000412, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (23/02/06 17:02), Yosry Ahmed wrote: [..] > > A 1/10 difference in ratio between fullness groups is intentional > > and critical for classes that have a high number of objs_per_zspage. > > For instance, class-624 stores 59 objects per zspage. With a 1/10 > > ratio grouping, the difference in inuse values between the page > > with the lowest and highest inuse in a single fullness group is > > only 4 objects (2469 bytes), whereas a 1/5 ratio grouping would > > result in a difference of 10 objects (6240 bytes). > > > The memory extra overhead would be sizeof(list_head) * nr of classes * > extra fullness groups = 16 * 255 * 6 = 24480 bytes ~= 24KB on a > machine with 4096 page size. Sounds reasonable (although I wonder how > it scales with PAGE_SIZE). It should be slightly lower than that. We never have 255 classes, because clases get merged. On a system with chain size of 10 we have 141 classes, with chain size of 8 it's 119 and chain size of 16 gives us 192 size classes. > > enum fullness_group { > > - ZS_EMPTY, > > - ZS_ALMOST_EMPTY, > > - ZS_ALMOST_FULL, > > - ZS_FULL, > > + ZS_USAGE_0, > > + ZS_USAGE_10, > > + ZS_USAGE_20, > > + ZS_USAGE_30, > > + ZS_USAGE_40, > > + ZS_USAGE_50, > > + ZS_USAGE_60, > > + ZS_USAGE_70, > > + ZS_USAGE_80, > > + ZS_USAGE_90, > > + ZS_USAGE_99, > > + ZS_USAGE_100, > > NR_ZS_FULLNESS, > > }; > > > > Is there a reason why this can't be done with something like #define > FULLNESS_GROUPS 10? We can make sure during build that (100 % > FULLNESS_GROUPS == 0) to make our lives easier. I feel like the code > will be much more concise and easier to navigate, instead of multiple > enums and static arrays. I wanted to keep things the way they are to make reviews simpler. We probably can do something more "disruptive" in a separate patch.