Hi Tejun and Yonghong, On Fri, May 20, 2022 at 12:42 PM Hao Luo <haoluo@xxxxxxxxxx> wrote: > > Hi Tejun and Yonghong, > > On Fri, May 20, 2022 at 9:45 AM Tejun Heo <tj@xxxxxxxxxx> wrote: > > On Fri, May 20, 2022 at 09:29:43AM -0700, Yonghong Song wrote: > > > <various stats interested by the user> > > > > > > This way, user space can easily construct the cgroup hierarchy stat like > > > cpu mem cpu pressure mem pressure ... > > > cgroup1 ... > > > child1 ... > > > grandchild1 ... > > > child2 ... > > > cgroup 2 ... > > > child 3 ... > > > ... ... > > > > > > the bpf iterator can have additional parameter like > > > cgroup_id = ... to only call bpf program once with that > > > cgroup_id if specified. > > Yep, this should work. We just need to make the cgroup_id parameter > optional. If it is specified when creating bpf_iter_link, we print for > that cgroup only. If it is not specified, we iterate over all cgroups. > If I understand correctly, sounds doable. > Yonghong, I realized that seek() which Tejun has been calling out, can be used to specify the target cgroup, rather than adding a new parameter. Maybe, we can pass cgroup_id to seek() on cgroup bpf_iter, which will instruct read() to return the corresponding cgroup's stats. On the other hand, reading without calling seek() beforehand will return all the cgroups. WDYT?
