On Tue, 2011-01-25 at 21:13 +0100, Peter Zijlstra wrote:
> On Tue, 2011-01-25 at 18:02 -0200, Glauber Costa wrote:
>
> > I fail to see how does clock_task influence cpu power.
> > If we also have to touch clock_task for better accounting of other
> > stuff, it is a separate story.
> > But for cpu_power, I really fail. Please enlighten me.
>
> static void update_rq_clock_task(struct rq *rq, s64 delta)
> {
> s64 irq_delta;
>
> irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
>
> if (irq_delta > delta)
> irq_delta = delta;
>
> rq->prev_irq_time += irq_delta;
> delta -= irq_delta;
> rq->clock_task += delta;
>
> if (irq_delta && sched_feat(NONIRQ_POWER))
> sched_rt_avg_update(rq, irq_delta);
> }
>
> its done through that sched_rt_avg_update() (should probably rename
> that), it computes a floating average of time not spend on fair tasks.
>
It creates a dependency on CONFIG_IRQ_TIME_ACCOUNTING, though.
This piece of code is simply compiled out if this option is disabled.
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