linux-kernel - Re: [RFC] SLUB - define OO_ macro instead of hardcoded numbers

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Date:	Wed, 22 Oct 2008 22:15:56 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] SLUB - define OO_ macro instead of hardcoded numbers

[Christoph Lameter - Wed, Oct 22, 2008 at 11:10:56AM -0700]
> On Wed, 22 Oct 2008, Cyrill Gorcunov wrote:
>
>> +#define OO_SHIFT	16
>> +#define OO_MASK		((1 << OO_SHIFT) - 1)
>> +#define MAX_OBJS_PER_PAGE	65535 /* see struct page.objects */
>
> This is == OO_MASK right? Otherwise things will break when we change  
> OO_SHIFT.
>

Yes, I set it 65535 directly to distinguish it from OO_MASK
meaning not value and point to page.objects since they are
u16. Which meant that is the point where all limits start.
So it we set OO_SHIFT to say 14 it will not be a problem
but if we exceed 16 bits it will break SLUB. Am I right?
(I become scratching the head :)

		- Cyrill -
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