linux-kernel - Re: [PATCH] mm: percpu: micro-optimize round-to-even

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Message-ID: <alpine.DEB.2.11.1406190925430.2785@gentwo.org>
Date:	Thu, 19 Jun 2014 09:29:52 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Tejun Heo <tj@...nel.org>
cc:	Rasmus Villemoes <linux@...musvillemoes.dk>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: percpu: micro-optimize round-to-even

On Thu, 19 Jun 2014, Tejun Heo wrote:

> On Thu, Jun 19, 2014 at 12:02:29PM +0200, Rasmus Villemoes wrote:
> > This change shaves a few bytes off the generated code.
> >
> > Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> > ---
> >  mm/percpu.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/mm/percpu.c b/mm/percpu.c
> > index 2ddf9a9..978097f 100644
> > --- a/mm/percpu.c
> > +++ b/mm/percpu.c
> > @@ -720,8 +720,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved)
> >  	if (unlikely(align < 2))
> >  		align = 2;
> >
> > -	if (unlikely(size & 1))
> > -		size++;
> > +	size += size & 1;
>
> I'm not gonna apply this.  This isn't that hot a path.  It's not
> worthwhile to micro optimize code like this.

Dont we have an ALIGN() macro for this?

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