On Wed 2022-04-27 16:40 +0200, Thomas Gleixner wrote: > On Wed, Apr 27 2022 at 12:50, Aaron Tomlin wrote: > > On Mon 2022-04-25 16:21 -0300, Marcelo Tosatti wrote: > >> Is there anything that prevents a nohz full CPU from running an > >> application with short and frequent idling? > > > > I'm not sure I understand the question; albeit, if I understand correctly, > > yes: the scheduling-clock tick, if it was stopped. > > Yet I believe this behaviour is correct. Consider the following example: > > > > When a CFS task is moved/or migrated to a nohz_full CPU that was > > previously idle and had its tick stopped, if its the only task on the > > run-queue then it is possible that the idle task may not restart the > > tick (see __tick_nohz_full_update_tick()). Thus once the CFS task exits > > manual intervention i.e. a reschedule IPI to wake the idle task, would be > > required to run again, on the same CPU. > > When the task exits and the tick was stopped, why should idle restart > the tick? There is nothing to do, so what? Hi Thomas, Indeed. As per my response, I do not see an issue. Perhaps I misunderstood Marcelo's question, no? Kind regards, -- Aaron Tomlin
