On Wed 22-03-23 11:20:55, Marcelo Tosatti wrote: > On Wed, Mar 22, 2023 at 02:35:20PM +0100, Michal Hocko wrote: [...] > > > "Performance details for the kworker interruption: > > > > > > oslat 1094.456862: sys_mlock(start: 7f7ed0000b60, len: 1000) > > > oslat 1094.456971: workqueue_queue_work: ... function=vmstat_update ... > > > oslat 1094.456974: sched_switch: prev_comm=oslat ... ==> next_comm=kworker/5:1 ... > > > kworker 1094.456978: sched_switch: prev_comm=kworker/5:1 ==> next_comm=oslat ... > > > > > > The example above shows an additional 7us for the > > > > > > oslat -> kworker -> oslat > > > > > > switches. In the case of a virtualized CPU, and the vmstat_update > > > interruption in the host (of a qemu-kvm vcpu), the latency penalty > > > observed in the guest is higher than 50us, violating the acceptable > > > latency threshold for certain applications." > > > > Yes, I have seen that but it doesn't really give a wider context to > > understand why those numbers matter. > > OK. > > "In the case of RAN, a MAC scheduler with TTI=1ms, this causes >100us > interruption observed in a guest (which is above the safety > threshold for this application)." > > Is that OK? This might be a sufficient information for somebody familiar with the matter (not me). So no, not enough. We need to hear a more complete story. -- Michal Hocko SUSE Labs
