On 19/10/16 12:25, Vincent Guittot wrote: > On 19 October 2016 at 11:46, Dietmar Eggemann <dietmar.eggem...@arm.com> > wrote: >> On 18/10/16 12:56, Vincent Guittot wrote: >>> Le Tuesday 18 Oct 2016 à 12:34:12 (+0200), Peter Zijlstra a écrit : >>>> On Tue, Oct 18, 2016 at 11:45:48AM +0200, Vincent Guittot wrote: >>>>> On 18 October 2016 at 11:07, Peter Zijlstra <pet...@infradead.org> wrote:
[...] >> But this test only makes sure that we don't see any ghost contribution >> (from non-existing cpus) any more. >> >> We should study the tg->se[i]->avg.load_avg for the hierarchy of tg's >> (with the highest tg having a task enqueued) a little bit more, with and >> without your v5 'sched: reflect sched_entity move into task_group's load'. > > Can you elaborate ? I try :-) I thought I will see some different behaviour because of the fact that the tg se's are initialized differently [1024 versus 0]. But I can't spot any difference. The test case is running a sysbench thread affine to cpu1 in tg_root/tg_1/tg_11/tg_111 on tip/sched/core on an ARM64 Juno (6 logical cpus). The moment the sysbench task is put into tg_111 tg_111->se[1]->avg.load_avg gets updated to 0 any way because of the huge time difference between creating this tg and attaching a task to it. So the tg->se[2]->avg.load_avg signals for tg_111, tg_11 and tg_1 look exactly the same w/o and w/ your patch. But your patch helps in this (very synthetic) test case as well. W/o your patch I see remaining tg->load_avg for tg_1 and tg_11 after the test case has finished because the tg's were exclusively used on cpu1. # cat /proc/sched_debug cfs_rq[1]:/tg_1 .tg_load_avg_contrib : 0 .tg_load_avg : 5120 (5 (unused cpus) * 1024 * 1) cfs_rq[1]:/tg_1/tg_11/tg_111 .tg_load_avg_contrib : 0 .tg_load_avg : 0 cfs_rq[1]:/tg_1/tg_11 .tg_load_avg_contrib : 0 .tg_load_avg : 5120 With your patch applied all the .tg_load_avg are 0.
