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Fri, 13 Jan 2023 09:32:23 -0800 (PST) Received: from google.com ([2620:15c:211:201:2e4e:fba:501b:3a8c]) by smtp.gmail.com with ESMTPSA id l6-20020a170903244600b0019467381dd6sm2392322pls.33.2023.01.13.09.32.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jan 2023 09:32:22 -0800 (PST) Date: Fri, 13 Jan 2023 09:32:21 -0800 From: Minchan Kim To: Sergey Senozhatsky Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv2 1/4] zsmalloc: rework zspage chain size selection Message-ID: References: <20230109033838.2779902-1-senozhatsky@chromium.org> <20230109033838.2779902-2-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230109033838.2779902-2-senozhatsky@chromium.org> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0A583180018 X-Rspam-User: X-Stat-Signature: 6xpz7fnpe7fy1w9b5dccux3xz88pytnb X-HE-Tag: 1673631144-463527 X-HE-Meta: U2FsdGVkX1/LG1RejVw3JzxxGa9ryv7ihPRovDfNQXxAoSK+kH8+9IKlV+cbAqnj+s6cqm6rh85NVpkSMPQkJxwwcljJK6NO/jeOpJfml3gN6Ebs3UoUp8pntmwH4BNnn1IAgvoo+o7te5JYvZ11asJm6gCKjEULdOLDW4HNPw/lxbQi+MUhJ8TcQDmsOf33Trb9s4i+zirTdSrEHMvF7ub5OcRfQznqEnsc7+Ue7Z65cUmkeYvmsEoZCUnM+hA1uQCZMexcrL9vqLN5f/W+hHiMxfmE9270IyTXTPOSehSNkCTZL+nmblY7fhQCj14wz+dhZ1PzejNc60EvUjBnkBQnKSCC57F/GQ+LQtJ9rHuQU42oE1g6zy3aZoXea6lBe1QiHJFf5vVJx+ltXKOHOw/CnFuB/oDuezGnhXxmStQdKEy6GeKFFBK5+zrzgmbOeVpOZrqU27Suo+crn6BvtWwgXpkxN2IDZrYmOyWrnL9G4fT7jsBVoUvkfDBzipQkRNMJmU8dcvl5seIN42LjiBpu1VE+THh5GHD9bY3+rofPO9rgPLo+ZM5ruAuP96/ZAIR0qM97xm0US2ou3AD3poNDAEvO4CD6p0aobQsKhVDlTsuYhBBfF3WjgOuSFCNMXk4HlCe/wi5h1u7YWak+T5eYG4EVxuxjtg/B2oIZEZ5FMrTGQARvOi/WNdrLvKv5NPAvWQDNxMs4hpA5k3gXHtz+DX2fOOuCZ6Rz1iRKhNIFeN8I5ln5ihFBisoCrGHfE2gpt3dZbJRgB1xk73mOe937Bxlh0zq0MjLPtui42eeL82kLqMRfbfww/SoxGX1KLNI8CmZluhjHcjDh2EtVduYUFUNbSa5gOiZs9uss298i+o3nRsO45ou5y562z2Mw6c6A7l4DliGLr0b0rI+DWB8gQU9eYoB6kJQg6mZb+lYMJ+SyhDtxyYOiH+wNxoSVmsgTLvXoc6+FBlfumhu G5zuj3wv Uh2Io6HBD+fj/cVRIhXtcdc37hqTiSTzOmpu5FDXxIZfe6tuDAlw5F9kh43aLj9udP1/UXyfw9wYFEGV2Ip5naq0cvCxCaoO4/6o328QktK4RW9hMJ5XVwhpcGXjjrDB4ksA+LrIk/FXYzofIHEmFFCCkLnTbyqCbYyDjcQafu6W5ucCk3/37mj8sP6naix9zrT6e5SeBq1XsxzEIOWE2rmS31BdimfpnI0cYHGTcqN4bGHM/dnfgqfqWbPNGRN6FVCH4vxDPZbgx4yp7I93OWPZcFvON+2AcvubIG5Q32oGctMg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.004970, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 09, 2023 at 12:38:35PM +0900, Sergey Senozhatsky wrote: > Computers are bad at division. We currently decide the best > zspage chain size (max number of physical pages per-zspage) > by looking at a `used percentage` value. This is not enough > as we lose precision during usage percentage calculations > For example, let's look at size class 208: > > pages per zspage wasted bytes used% > 1 144 96 > 2 80 99 > 3 16 99 > 4 160 99 > > Current algorithm will select 2 page per zspage configuration, > as it's the first one to reach 99%. However, 3 pages per zspage > waste less memory. > > Change algorithm and select zspage configuration that has > lowest wasted value. > > Signed-off-by: Sergey Senozhatsky Acked-by: Minchan Kim