linux-kernel - Re: [tip:sched/core] sched: Untangle cpu-load and timekeeping code

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Message-ID: <AANLkTinM8oeCSxRfj=WQPc1-6W05O0XmvDK0Hde6zckL@mail.gmail.com>
Date:	Thu, 27 Jan 2011 14:55:30 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched: Untangle cpu-load and timekeeping code

On Thu, Jan 27, 2011 at 4:03 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>> We should not do this checking any more. In normal case,
>> it will always return false.
>> If it indeed returns true for some reason, we will lose the
>> timer forever.
>
> Its needed for the nohz case, arguably we could move it inside
> calc_global_nohz().

I have no idea why we need that checking in  calc_global_nohz().

Before this patch, time_before(jiffies, calc_load_update) is
needed in calc_global_nohz() because it will reduce the ovehead
on dealing with calc_load_fold_idle if we have idle dance in one
LOAD_FREQ.

Now we have calc_global_load() called at every LOAD_FREQ
instead of every tick, that problem is gone.

But maybe I have missed something ;)

Thanks,
Yong


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