On 08/29/2017 01:43 PM, Tejun Heo wrote: > In cgroup1, while cpuacct isn't actually controlling any resources, it > is a separate controller due to combination of two factors - > 1. enabling cpu controller has significant side effects, and 2. we > have to pick one of the hierarchies to account CPU usages on. cpuacct > controller is effectively used to designate a hierarchy to track CPU > usages on. > > cgroup2's unified hierarchy removes the second reason and we can > account basic CPU usages by default. While we can use cpuacct for > this purpose, both its interface and implementation leave a lot to be > desired - it collects and exposes two sources of truth which don't > agree with each other and some of the exposed statistics don't make > much sense. Also, it propagates all the way up the hierarchy on each > accounting event which is unnecessary. > > This patch adds basic resource accounting mechanism to cgroup2's > unified hierarchy and accounts CPU usages using it. > > * All accountings are done per-cpu and don't propagate immediately. > It just bumps the per-cgroup per-cpu counters and links to the > parent's updated list if not already on it. > > * On a read, the per-cpu counters are collected into the global ones > and then propagated upwards. Only the per-cpu counters which have > changed since the last read are propagated. > > * CPU usage stats are collected and shown in "cgroup.stat" with "cpu." > prefix. Total usage is collected from scheduling events. User/sys > breakdown is sourced from tick sampling and adjusted to the usage > using cputime_adjust(). > > This keeps the accounting side hot path O(1) and per-cpu and the read > side O(nr_updated_since_last_read). > > v2: Minor changes and documentation updates as suggested by Waiman and > Roman. > > Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Li Zefan <lizefan@xxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Waiman Long <waiman.long@xxxxxxx> I just noticed that you have used my obsoleted email address in the cc line. Would you mind changing it to the one that I am currently using? Thanks, Longman -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
