Messages in this thread | | | Date | Fri, 24 Mar 2017 15:00:15 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC v5 5/9] sched/deadline: do not reclaim the whole CPU bandwidth |
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On Fri, Mar 24, 2017 at 04:52:58AM +0100, luca abeni wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 20c62e7..efa88eb 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6716,6 +6716,12 @@ static void sched_dl_do_global(void) > raw_spin_unlock_irqrestore(&dl_b->lock, flags); > > rcu_read_unlock_sched(); > + if (dl_b->bw == -1) > + cpu_rq(cpu)->dl.deadline_bw_inv = 1 << 8; > + else > + cpu_rq(cpu)->dl.deadline_bw_inv = > + to_ratio(global_rt_runtime(), > + global_rt_period()) >> 12;
Coding style requires braces here (on both legs of the condition)..
Also, I find deadline_bw_inv an awkward name; would something like bw_ratio or so be more accurate?
> + if (global_rt_runtime() == RUNTIME_INF) > + dl_rq->deadline_bw_inv = 1 << 8; > + else > + dl_rq->deadline_bw_inv = > + to_ratio(global_rt_runtime(), global_rt_period()) >> 12;
That's almost the same code; do we want a helper function?
> > u64 grub_reclaim(u64 delta, struct rq *rq) > { > + return (delta * rq->dl.running_bw * rq->dl.deadline_bw_inv) >> 20 >> 8; > }
At which point we might want a note about how this doesn't overflow I suppose.
Also:
delta *= rq->dl.running_bw; delta *= rq->dl.bw_ratio; delta >>= 20 + 8;
return delta;
Might be more readable ?
Alternatively:
delta = (delta * rq->dl.running_bw) >> 8; delta = (delta * rq->dl.bw_ratio) >> 20;
return delta;
But I doubt we care about those extra 8 bit of space; delta should not be over 36 bits (~64 seconds) anyway I suppose.
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