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AJvYcCU8wnA6e+YxtVPMO2s5rGHmzvlsvCtkoNyeXRPpg8Cxx2gCZPBipltXHCnGuuBitMzX7kc8GQo5ZlKYxe9FXUigYFE= X-Gm-Message-State: AOJu0YyqUHH44j+lGFygiq2J1awB4eWI9mpZJnNvsiGXslUl7OBGNaBg QDCPfxH9SDJMkTLpcfzYsCu5Vn5JPsTGzvRwjo0zchQcZsAv8qEyICFT8rmSocvCnfVu5bJoy9v yk3VxtH7jJ4EANm6QCPkGVjyJzWc= X-Google-Smtp-Source: AGHT+IF7DzPWIdcQI0xDVXGNgiqETlF0CcM6aC1lJ7ACKSiX8Eh1ei7x7iwd4JliMYzB+ZO5Z7jLHgHu+ersMMXDcQ0= X-Received: by 2002:a05:6214:3d9d:b0:6af:c66a:d5a8 with SMTP id 6a1803df08f44-6b059f65400mr21667096d6.51.1717752373411; Fri, 07 Jun 2024 02:26:13 -0700 (PDT) MIME-Version: 1.0 References: <20240606165303.431215-1-flintglass@gmail.com> In-Reply-To: <20240606165303.431215-1-flintglass@gmail.com> From: Nhat Pham Date: Fri, 7 Jun 2024 10:26:02 +0100 Message-ID: Subject: Re: [PATCH] mm: zswap: limit number of zpools based on CPU and RAM To: Takero Funaki Cc: Johannes Weiner , Yosry Ahmed , Chengming Zhou , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 753D44000D X-Stat-Signature: jop37tswqrmnxemr1fcuthpsm1np184s X-HE-Tag: 1717752374-715078 X-HE-Meta: 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 AkborARN VFiqIaTCRggfEBdiCiclwuVvWVadyFc1oGhtV0vkimQ2fOKrLU9jNIyJDQyKBULfMU9ujgL9k1/k/Nd9gZ3PC6xOy8sdxE93LfJa6XZsw6j0d3sjt5ly1qW+Zt6Rf+MYkGIN29VzV0yWbu80ndSd8QAI2YmX/a00NBUb/A7tj+8URTd9/yaKSq8I1iAdT+vPLw3ZjolDLWqNtjMiaVDwchTG0lKMT7R3C54l9LedUDSSn4wefEh0MWnVbEmtz1eRkSWQBSqn1+sUIAXdZtkFG+z/a8EExMXDw0kuTjFbfTgWnY2OjDVIh1IREai/nwwUDAyH1yc/Mzw+3ETpeY4C9WHesHSliZDKXBHA9rIUmFf5+JmtwDCVXIDNOzA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000654, 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 Thu, Jun 6, 2024 at 5:53=E2=80=AFPM Takero Funaki = wrote: > > This patch limits the number of zpools used by zswap on smaller systems. > > Currently, zswap allocates 32 pools unconditionally. This was > implemented to reduce contention on per-zpool locks. However, it incurs > allocation overhead by distributing pages across pools, wasting memory > on systems with fewer CPUs and less RAM. > > This patch allocates approximately 2*CPU zpools, with a minimum of 1 > zpool for single-CPU systems and up to 32 zpools for systems with 16 or > more CPUs. This number is sufficient to keep the probability of > busy-waiting by a thread under 40%. The upper limit of 32 zpools remains > unchanged. > > For memory, it limits to 1 zpool per 60MB of memory for the 20% default > max pool size limit, assuming the best case with no fragmentation in > zspages. It expects 90% pool usage for zsmalloc. > > Signed-off-by: Takero Funaki > --- I think this needs benchmarking. Theoretical justification is nice, but I'm not convinced it'll translate neatly to the messy world of real life systems.