Re: [patch v5 06/15] sched: log the cpu utilization at rq

From: Alex Shi
Date: Fri Mar 22 2013 - 04:50:03 EST

On 02/20/2013 11:22 PM, Peter Zijlstra wrote:
> On Wed, 2013-02-20 at 22:33 +0800, Alex Shi wrote:
>>> You don't actually compute the rq utilization, you only compute the
>>> utilization as per the fair class, so if there's significant RT
>> activity
>>> it'll think the cpu is under-utilized, whihc I think will result in
>> the
>>> wrong thing.
>> yes. A bit complicit to resolve this. Any suggestions on this, guys?
> Shouldn't be too hard seeing as we already track cpu utilization for !
> fair usage; see rq::rt_avg and scale_rt_power.

Hi Peter,

rt_avg will be accumulated the irq time and steal time in
update_rq_clock_task(), if CONFIG_IRQ_TIME_ACCOUNTING or
CONFIG_IRQ_TIME_ACCOUNTING defined. That cause irq/steal time was double
added into rq utilisation, since normal rq->util already include the irq
time. So we do wrongly judgement to think it is a overload cpu. but it
is not.

To resolve this issue, if is it possible to introduce another member in
rq to describe rt_avg non irq/steal beside the rt_avg? If so, what the
name do you like to use?

Thanks Alex
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