From: Peter Zijlstra <peterz@infradead.org>
To: stephan.baerwolf@tu-ilmenau.de
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
ncrao@google.com
Subject: Re: sched: fix/optimise some issues
Date: Wed, 20 Jul 2011 21:11:33 +0200 [thread overview]
Message-ID: <1311189093.29152.74.camel@twins> (raw)
In-Reply-To: <4E26DB41.9070002@tu-ilmenau.de>
On Wed, 2011-07-20 at 15:42 +0200, Stephan Bärwolf wrote:
> "entity_key()" is only used in "__enqueue_entity()" and
> its only function is to subtract a tasks vruntime by
> its groups minvruntime.
> Before this patch a rbtree enqueue-decision is done by
> comparing two tasks in the style:
>
> "if (entity_key(cfs_rq, se) < entity_key(cfs_rq, entry))"
>
> which would be
>
> "if (se->vruntime-cfs_rq->min_vruntime < entry->vruntime-cfs_rq->min_vruntime)"
>
> or (if reducing cfs_rq->min_vruntime out)
>
> "if (se->vruntime < entry->vruntime)"
>
> which is
>
> "if (entity_before(se, entry))"
>
> So we do not need "entity_key()".
> If "entity_before()" is inline we will also save one subtraction (only one,
> because "entity_key(cfs_rq, se)" was cached in "key")
Indeed, thanks!
next prev parent reply other threads:[~2011-07-20 19:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-20 13:42 sched: fix/optimise some issues Stephan Bärwolf
2011-07-20 19:11 ` Peter Zijlstra
2011-07-21 1:00 ` Mike Galbraith
2011-07-20 19:11 ` Peter Zijlstra [this message]
2011-07-20 19:11 ` Peter Zijlstra
2011-07-21 15:08 ` Peter Zijlstra
2011-07-21 16:36 ` Stephan Bärwolf
2011-07-21 16:32 ` Peter Zijlstra
2011-07-21 16:43 ` Peter Zijlstra
2011-07-21 16:51 ` Peter Zijlstra
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