On 23 August 2016 at 16:13, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Aug 23, 2016 at 03:28:19PM +0200, Vincent Guittot wrote: >> I still wonder if using a flat util hierarchy is the right solution to >> solve this problem with utilization and task group. I have noticed >> exact same issues with load that generates weird task placement >> decision and i think that we should probably try to solve both wrong >> behavior with same mechanism. but this is not possible with flat >> hierarchy for load >> >> Let me take an example. >> TA is a always running task on CPU1 in group /root/level1/ >> TB wakes up on CPU0 and moves TA into group /root/level2/ >> Even if TA stays on CPU1, runnable_load_avg of CPU1 root cfs rq will become >> 0. > > Because while we migrate the load_avg on /root/level2, we do not > propagate the load_avg up the hierarchy?
yes. At now, the load of a cfs_rq and the load of its sched_entity that represents it at parent level are disconnected > > And always propagating everyrthing up will indeed also fix the > utilization issue. > > Of course, doing that propagation has its costs.. yes, that's the counterpart > > Didn't you post a patch doing just this a while ago? My patch was doing that but only for utilization and i have start to work on adding the propagation of load as well
