On Thu, Mar 31, 2022 at 11:42 AM Tim Chen wrote: > > On Wed, 2022-03-30 at 17:46 +0800, kernel test robot wrote: > > > > Greeting, > > > > FYI, we noticed a -25.9% regression of hackbench.throughput due to commit: > > > > Will try to check the regression seen. > Double check that the regression could be reproduced on top of the latest sched/core branch: parent ("sched/fair: Don't rely on ->exec_start for migration") fbc ("sched/fair: Simple runqueue order on migrate") parent fbc 91107 -40.8% 53897 hackbench.throughput and it is consistent with lkp's original report that the context switch count is much higher with patch applied: 9591919 +510.3% 58534937 hackbench.time.involuntary_context_switches 36451523 +281.5% 1.391e+08 hackbench.time.voluntary_context_switches Considering that this patch 'raises' the priority of the migrated task, by giving it the cfs_rq->min_vruntime, it is possible that the migrated task would preempt the current running task more easily. 0.00 +12.2 12.21 perf-profile.calltrace.cycles-pp.enqueue_entity.enqueue_task_fair.ttwu_do_activate.try_to_wake_up.autoremove_wake_function and the patched version has spent more time on enqueue_entity(), which might be caused by setting sched entity hierarchy from leaf to root, which was mentioned in another thread. -- Thanks, Chenyu