On Thu, Apr 21, 2016 at 2:33 PM, Peter Zijlstra <[email protected]> wrote: > On Thu, Apr 21, 2016 at 09:09:43AM +0800, Wanpeng Li wrote: >> >> Sometimes .update_curr hook is called w/o tasks actually running, it is >> >> captured by: >> >> >> >> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; >> >> >> >> We should not trigger cpufreq update in this case for rt/deadline >> >> classes, and this patch fix it. > >> I add a print to print when delta_exec is zero for rt class, something > > So its zero, so what? > >> like below: > >> watchdog/5-48 [005] d... 568.449105: update_curr_rt: rt >> delta_exec is zero >> watchdog/5-48 [005] d... 568.449111: <stack trace> >> => put_prev_task_rt >> => pick_next_task_idle > > So we'll go idle, but as of this point we're still running the rt task.
Skipping the update in that case might be the right thing to do, though. It doesn't matter in 4.6-rc, because the current governors don't use util/max anyway, so they just get an extra call they can use to evaluate things. However, it matters for schedutil, because it will (over)react to the special util/max combination then. So this looks like a change to make in 4.7.
