lkml.org 
[lkml]   [2016]   [Feb]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks
    On Tue, Feb 09, 2016 at 05:02:33PM -0800, Steve Muckle wrote:
    > > Index: linux-pm/kernel/sched/deadline.c
    > > ===================================================================
    > > --- linux-pm.orig/kernel/sched/deadline.c
    > > +++ linux-pm/kernel/sched/deadline.c
    > > @@ -1197,6 +1197,9 @@ static void task_tick_dl(struct rq *rq,
    > > {
    > > update_curr_dl(rq);
    > >
    > > + /* Kick cpufreq to prevent it from stalling. */
    > > + cpufreq_kick();
    > > +
    > > /*
    > > * Even when we have runtime, update_curr_dl() might have resulted in us
    > > * not being the leftmost task anymore. In that case NEED_RESCHED will
    >
    > I think additional hooks such as enqueue/dequeue would be needed in
    > RT/DL. The task tick callbacks will only run if a task in that class is
    > executing at the time of the tick. There could be intermittent RT/DL
    > task activity in a frequency domain (the only task activity there, no
    > CFS tasks) that doesn't happen to overlap the tick. Worst case the task
    > activity could be periodic in such a way that it never overlaps the tick
    > and the update is never made.

    No, for RT (RR/FIFO) we do not have enough information to do anything
    useful. Basically RR/FIFO should result in running 100% whenever we
    schedule such a task.

    That means RR/FIFO want a hook in pick_next_task_rt() to bump the freq
    to 100% and leave it there until something else gets to run.

    For DL it basically wants to set a minimum freq based on reserved
    utilization, so that is __setparam_dl() or somewhere around there.

    And we should either use CPPC hints for min freq or manually ensure that
    the CFS callback will not select something less than this.

    \
     
     \ /
      Last update: 2016-02-11 13:21    [W:7.975 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site