Re: [PATCH 16/16] KVM-GST: adjust scheduler cpu power

[Peter Zijlstra <peterz@infradead.org>]

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.