On 30/03/17 22:13, Rafael J. Wysocki wrote: > On Thu, Mar 30, 2017 at 10:58 AM, Juri Lelli <[email protected]> wrote: > > Hi, > > Hi, > > > On 30/03/17 00:41, Rafael J. Wysocki wrote: > >> On Friday, March 24, 2017 02:08:59 PM Juri Lelli wrote: > >> > No assumption can be made upon the rate at which frequency updates get > >> > triggered, as there are scheduling policies (like SCHED_DEADLINE) which > >> > don't trigger them so frequently. > >> > > >> > Remove such assumption from the code. > >> > >> But the util/max values for idle CPUs may be stale, no? > >> > > > > Right, that might be a problem. A proper solution I think would be to > > remotely update such values for idle CPUs, and I believe Vincent is > > working on a patch for that. > > > > As mid-term workarounds, changing a bit the current one, come to my > > mind: > > > > - consider TICK_NSEC (continue) only when SCHED_CPUFREQ_DL is not set > > - remove CFS contribution (without triggering a freq update) when a CPU > > enters IDLE; this might not work well, though, as we probably want > > to keep in blocked util contribution for a bit > > > > What you think is the way to go? > > Well, do we want SCHED_DEADLINE util contribution to be there even for > idle CPUs? >
DEADLINE util contribution is removed, even if the CPU is idle, by the reclaiming mechanism when we know (applying GRUB algorithm rules [1]) that it can't be used anymore by a task (roughly speaking). So, we shouldn't have this problem in the DEADLINE case. [1] https://marc.info/?l=linux-kernel&m=149029880524038
