linux-kernel - Re: [patch v7 05/21] sched: log the cpu utilization at rq

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Message-ID: <5187A397.9040102@intel.com>
Date:	Mon, 06 May 2013 20:35:35 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Phil Carmody <pc+lkml@...f.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [patch v7 05/21] sched: log the cpu utilization at rq

On 05/06/2013 08:03 PM, Phil Carmody wrote:
>> > +     period = rq->avg.runnable_avg_period ? rq->avg.runnable_avg_period : 1;
>> > +     rq->util = (u64)(rq->avg.runnable_avg_sum << SCHED_POWER_SHIFT)
>> > +                             / period;
> Greetings, Alex.
> 
> That cast achieves nothing where it is. If the shift has overflowed,
> then you've already lost information; and if it can't overflow, then
> it's not needed at all. 
> 
> It's itsy-bitsy, but note that there exists a div_u64(u64 dividend,
> u32 divisor) helper which may be implemented to be superior to just '/'.
> (And also note that the assignment to ``period'' is a good candidate for
> gcc's ``?:'' operator.)
> 
> If you pull the cast inside the brackets, then you may add my
> Reviewed-by: Phil Carmody <pc+lkml@...f.org>

You are right, Phil!
Thanks for review! :)

-- 
Thanks
    Alex
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