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Fri, 13 Feb 2026 01:42:22 -0800 (PST) From: Jialin Wang To: wjl.linux@gmail.com Cc: axboe@kernel.dk, cgroups@vger.kernel.org, josef@toxicpanda.com, lianux.mm@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, tj@kernel.org Subject: Re: [RFC PATCH] blk-iocost: introduce 'linear-max' cost model for cloud disk Date: Fri, 13 Feb 2026 17:42:18 +0800 Message-ID: <20260213094218.253536-1-wjl.linux@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260213073829.182168-1-wjl.linux@gmail.com> References: <20260213073829.182168-1-wjl.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > This formula correctly models the dual-bucket behavior of cloud disks. > It ensures that for any block size, the calculated cost aligns with the > actual bottleneck (IOPS or BPS). This allows the system to reach close > to the provisioned BPS/IOPS limits without premature throttling, while > still maintaining the latency protection benefits of iocost. This model still has some limitations. Under workloads with mixed IO sizes and vrate max at 100%, it fail to fully saturate the hardware performance. However, it still demonstrates a clear improvement over the linear model. The following fio benchmarks were conducted with two cgroups assigned equal weights: Cgroup A: fio --bs=32k ... Cgroup B: fio --bs=1M ... Results: Model | Cgroup A (32k) | Cgroup B (1M) | Total ------------+------------------------+----------------------|---------------------- linear | 1137 IOPS (35.5 MiB/s) | 79 IOPS (79.5 MiB/s) | 1216 IOPS 115.0 MiB/s linear-max | 1781 IOPS (55.7 MiB/s) | 83 IOPS (83.9 MiB/s) | 1864 IOPS 139.6 MiB/s