On Mon, Aug 07, 2023 at 11:29:30AM +0800, Hao Jia wrote: > The member variable bstat of the structure cgroup_rstat_cpu > records the per-cpu time of the cgroup itself, but does not > include the per-cpu time of its descendants. The per-cpu time > 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 subtree_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/drgn, etc. > And we are still trying to determine how to expose it in the > cgroupfs interface. > > Suggested-by: Tejun Heo <tj@xxxxxxxxxx> > Signed-off-by: Hao Jia <jiahao.os@xxxxxxxxxxxxx> Applied to cgroup/for-6.6. Thanks. -- tejun
