Re: sched: fix/optimise some issues
From: Peter Zijlstra
Date: Wed Jul 20 2011 - 15:11:59 EST
On Wed, 2011-07-20 at 15:42 +0200, Stephan BÃrwolf 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")
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