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Message-ID: <441AC25E.1050504@yahoo.com.au>
Date: Sat, 18 Mar 2006 01:06:22 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Andreas Mohr <andi@rhlx01.fht-esslingen.de>
CC: Con Kolivas <kernel@kolivas.org>, ck@vds.kolivas.org,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [ck] Re: [PATCH] sched: activate SCHED BATCH expired
References: <200603081013.44678.kernel@kolivas.org> <200603172338.10107.kernel@kolivas.org> <441AB8FA.10609@yahoo.com.au> <200603180036.11326.kernel@kolivas.org> <20060317134740.GA7121@rhlx01.fht-esslingen.de>
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Andreas Mohr wrote:
> Hi,
> 
> On Sat, Mar 18, 2006 at 12:36:10AM +1100, Con Kolivas wrote:
> 
>>I'm not attached to the style, just the feature. If you think it's warranted 
>>I'll change it.
> 
> 
> Seconded.
> 
> An even nicer way (this solution seems somewhat asymmetric) than
> 
>    prio_array_t *target = rq->active;
>    if (batch_task(p))
>      target = rq->expired;
>    enqueue_task(p, target);
> 
> may be
> 
>    prio_array_t *target;
>    if (batch_task(p))
>      target = rq->expired;
>    else
>      target = rq->active;
>    enqueue_task(p, target);
> 

It doesn't actually generate the same code here (I guess it is good
that gcc gives us this control).

I think my way is (ever so slightly) better because it gets the load
going earlier and comprises one less conditional jump (admittedly in
the slowpath). You'd probably never be able to measure a difference
between any of the variants, however ;)

-- 
SUSE Labs, Novell Inc.
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