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Date: Wed, 22 Oct 2008 22:15:56 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] SLUB - define OO_ macro instead of hardcoded numbers
Message-ID: <20081022181556.GM9639@localhost>
References: <20081022161836.GG9639@localhost> <Pine.LNX.4.64.0810220926130.7633@quilx.com> <20081022163530.GH9639@localhost> <20081022165354.GI9639@localhost> <20081022172103.GJ9639@localhost> <Pine.LNX.4.64.0810221037320.7633@quilx.com> <48FF6800.20705@cs.helsinki.fi> <20081022175827.GL9639@localhost> <Pine.LNX.4.64.0810221110060.27088@quilx.com>
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[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 -