linux-kernel - Re: [PATCH 2/2 v4] sched: Rewrite per entity runnable load average tracking

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Message-ID: <20140729005640.GA5203@intel.com>
Date:	Tue, 29 Jul 2014 08:56:41 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org, pjt@...gle.com,
	bsegall@...gle.com, arjan.van.de.ven@...el.com,
	len.brown@...el.com, rafael.j.wysocki@...el.com,
	alan.cox@...el.com, mark.gross@...el.com, fengguang.wu@...el.com
Subject: Re: [PATCH 2/2 v4] sched: Rewrite per entity runnable load average
 tracking

On Mon, Jul 28, 2014 at 12:48:37PM +0200, Peter Zijlstra wrote:
> > +static __always_inline u64 decay_load(u64 val, u64 n)
> > +{
> > +	if (likely(val <= UINT_MAX))
> > +		val = decay_load32(val, n);
> > +	else {
> > +		val *= (u32)decay_load32(1 << 15, n);
> > +		val >>= 15;
> > +	}
> > +
> > +	return val;
> > +}
> 
> Please just use mul_u64_u32_shr().
> 
> /me continues reading the rest of it..

Good. Since 128bit is considered in mul_u64_u32_shr, load_sum can
afford more tasks :)
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