Hello, On Mon, Sep 13, 2021 at 12:40:06PM -0700, Shakeel Butt wrote: > I did one more experiment with same workload but with system_wq > instead system_unbound_wq and there is clear difference in profile: > > With system_unbound_wq: > - 4.63% 0.33% mmap [kernel.kallsyms] [k] queue_work_on > 4.29% queue_work_on > - __queue_work > - 3.45% wake_up_process > - try_to_wake_up > - 2.46% ttwu_queue > - 1.66% ttwu_do_activate > - 1.14% activate_task > - 0.97% enqueue_task_fair > enqueue_entity > > With system_wq: > - 1.36% 0.06% mmap [kernel.kallsyms] [k] queue_work_on > 1.30% queue_work_on > - __queue_work > - 1.03% wake_up_process > - try_to_wake_up > - 0.97% ttwu_queue > 0.66% ttwu_do_activate > > Tejun, is this expected? i.e. queuing work on system_wq has a > different performance impact than on system_unbound_wq? Yes, system_unbound_wq is putting the work item on the global shared workqueue while the system_wq is per-cpu, so on a loaded system, overhead difference showing up isn't too surprising. Thanks. -- tejun
