On 31/03/17 11:03, Rafael J. Wysocki wrote: > On Fri, Mar 31, 2017 at 9:31 AM, Juri Lelli <[email protected]> wrote: > > 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 > > OK > > Why don't you store the contributions from DL and CFS separately, then > (say, as util_dl, util_cfs, respectively) and only discard the CFS one > if delta_ns > TICK_NSEC?
Sure, this should work as well. I'll try this approach for next version. Thanks, - Juri
