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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6ab75ffsm1502885ad.175.2024.07.08.11.08.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Jul 2024 11:08:22 -0700 (PDT) Sender: Tejun Heo Date: Mon, 8 Jul 2024 08:08:20 -1000 From: Tejun Heo To: Cheng Yu Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, changhuaixin@linux.alibaba.com, shanpeic@linux.alibaba.com, dtcccc@linux.alibaba.com, vishalc@linux.ibm.com, linux-kernel@vger.kernel.org, zhangqiao22@huawei.com, judy.chenhui@huawei.com, yusongping@huawei.com, zhaowenhui8@huawei.com Subject: Re: [PATCH v2] sched/fair: set burst to 0 when remove the restriction on cfs bandwidth Message-ID: References: <20240708120053.861037-1-serein.chengyu@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240708120053.861037-1-serein.chengyu@huawei.com> Hello, On Mon, Jul 08, 2024 at 08:00:53PM +0800, Cheng Yu wrote: > From: Zhao Wenhui > > In the cpu subsystem of cgroup v1 and v2, we set the restriction on cfs > bandwidth by setting the quota and burst value. Later, when we remove > the restriction by setting the quota to the default value, the burst > value should also be forced to the its default value of zero. Explaining a bit why burst value should become zero can be helpful - ie. what happens when quota is not set but burst is limited? ... > @@ -10840,6 +10840,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota, > burst + quota > max_cfs_runtime)) > return -EINVAL; > > + /* > + * Ensure burst equals to zero when quota is -1. > + */ > + if (quota == RUNTIME_INF && burst) > + return -EINVAL; This happening would be a bug, right? Would it make more sense to use WARN_ON_ONCE()? Thanks. -- tejun