linux-kernel - Re: [PATCH 3/7] slub: Do not use c->page on free

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Message-ID: <alpine.DEB.2.11.1412101107350.6291@gentwo.org>
Date:	Wed, 10 Dec 2014 11:08:28 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Pekka Enberg <penberg@...nel.org>
cc:	akpm <akpm@...uxfoundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, iamjoonsoo@....com,
	Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH 3/7] slub: Do not use c->page on free

On Wed, 10 Dec 2014, Pekka Enberg wrote:

> > +static bool same_slab_page(struct kmem_cache *s, struct page *page, void *p)
>
> Why are you passing a pointer to struct kmem_cache here? You don't
> seem to use it.

True.
> > +{
> > +       long d = p - page->address;
> > +
> > +       return d > 0 && d < (1 << MAX_ORDER) && d < (compound_order(page) << PAGE_SHIFT);
> > +}
>
> Can you elaborate on what this is doing? I don't really understand it.

Checks if the pointer points to the slab page. Also it tres to avoid
having to call compound_order needlessly. Not sure if that optimization is
worth it.



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