linux-kernel - Re: [PATCH 4/6] rbtree: faster augmented insert

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Date:	Fri, 27 Jul 2012 22:04:26 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	riel@...hat.com, daniel.santos@...ox.com, aarcange@...hat.com,
	dwmw2@...radead.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] rbtree: faster augmented insert

On Fri, 2012-07-20 at 05:31 -0700, Michel Lespinasse wrote:
> +static void augment_rotate(struct rb_node *rb_old, struct rb_node *rb_new)
> +{
> +       struct test_node *old = rb_entry(rb_old, struct test_node, rb);
> +       struct test_node *new = rb_entry(rb_new, struct test_node, rb);
> +
> +       /* Rotation doesn't change subtree's augmented value */
> +       new->augmented = old->augmented;
> +       old->augmented = augment_recompute(old);
> +} 

> +static inline void augment_propagate(struct rb_node *rb)
> +{
> +       while (rb) {
> +               struct test_node *node = rb_entry(rb, struct test_node, rb);
> +               node->augmented = augment_recompute(node);
> +               rb = rb_parent(&node->rb);
> +       }
> +}

So why do we have to introduce these two new function pointers to pass
along when they can both be trivially expressed in the old single
augment function?


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