Re: [RFCv5 PATCH 30/46] sched: Add cpu capacity awareness to wakeup balancing

Peter Zijlstra
2015-08-13T18:24:15Z

On Tue, Jul 07, 2015 at 07:24:13PM +0100, Morten Rasmussen wrote:
>
> This patch adds capacity awareness to find_idlest_{group,queue} (used by
> SD_BALANCE_{FORK,EXEC}) such that groups/cpus that can accommodate the
> waking task based on task utilization are preferred. In addition, wakeup
> of existing tasks (SD_BALANCE_WAKE) is sent through
> find_idlest_{group,queue} if the task doesn't fit the capacity of the
> previous cpu to allow it to escape (override wake_affine) when
> necessary instead of relying on periodic/idle/nohz_idle balance to
> eventually sort it out.
>

That's policy not guided by the energy model.. Also we need something
clever for the wakeup balancing, the current stuff all stinks :/