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

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Date:	Tue, 16 Dec 2014 19:34:37 +0400
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, akpm@...uxfoundation.org,
	rostedt@...dmis.org, LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH 3/7] slub: Do not use c->page on free

2014-12-16 18:15 GMT+03:00 Jesper Dangaard Brouer <brouer@...hat.com>:
> On Tue, 16 Dec 2014 08:53:08 -0600 (CST)
> Christoph Lameter <cl@...ux.com> wrote:
>
>> On Tue, 16 Dec 2014, Joonsoo Kim wrote:
>>
>> > > Like this:
>> > >
>> > >         return d > 0 && d < page->objects * s->size;
>> > >
>> >
>> > Yes! That's what I'm looking for.
>> > Christoph, how about above change?
>>
>> Ok but now there is a multiplication in the fast path.
>
> Could we pre-calculate the value (page->objects * s->size) and e.g store it
> in struct kmem_cache, thus saving the imul ?
>

No, one kmem_cache could have several pages with different orders,
therefore different page->objects.

> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Sr. Network Kernel Developer at Red Hat
>   Author of http://www.iptv-analyzer.org
>   LinkedIn: http://www.linkedin.com/in/brouer
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