Hello, On Mon, Jul 17, 2023 at 05:36:12PM +0800, Hao Jia wrote: > Now the member variable bstat of the structure cgroup_rstat_cpu You said "now" indicating that the behavior has changed recently but I don't see what changed there. Can you elaborate? > records the per-cpu time of the cgroup itself, but does not > include the per-cpu time of its descendants. The per-cpu time It does. The per-cpu delta is added to its parent and then that will in turn be used to propagate to its parent. > including descendants is very useful for calculating the > per-cpu usage of cgroups. > > Although we can indirectly obtain the total per-cpu time > of the cgroup and its descendants by accumulating the per-cpu > bstat of each descendant of the cgroup. But after a child cgroup > is removed, we will lose its bstat information. This will cause > the cumulative value to be non-monotonic, thus affecting > the accuracy of cgroup per-cpu usage. > > So we add the cumul_bstat variable to record the total > per-cpu time of this cgroup and its descendants, which is > similar to "cpuacct.usage*" in cgroup v1. And this is > also helpful for the migration from cgroup v1 to cgroup v2. > After adding this variable, we can obtain the per-cpu time of > cgroup and its descendants in user mode through eBPF, etc. I think you're misunderstanding how the code works. Can you please double check? Thanks. -- tejun
