linux-kernel - Re: [PATCH] x86: mtrr cleanup for converting continuous to discrete

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Date:	Thu, 01 May 2008 14:10:58 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gabriel C <nix.or.die@...glemail.com>,
	Mika Fischer <mika.fischer@...pnet.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: mtrr cleanup for converting continuous to discrete
 - auto detect v2

Yinghai Lu wrote:
> On Thu, May 1, 2008 at 12:42 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> Yinghai Lu wrote:
>>
>>> loop mtrr chunk_size and gran_size from 1M to 2G to find out optimal
>> value.
>>  Why stopping at 2 GB?
> 
> if you select 4g for chunk size, we don't need to convert that from
> continuous to discrete to make X server driver happen.
> 
> actually the code could support any chunk_size...
> 
> for example: 16 g system
> orginal:
> 0-4g WB
> 3.5g-4g UC
> 4g-8g WB
> 8g-16g WB
> 16g-16.5g WB
> 
> if you set chunk size to 16g, and gran size <= 512M
> you will get
> 0-16g WB
> 3.5g-4g UC
> 16g-16.5g WB
> 

Yes, 16 GB systems are already mainstream; 32 GB is common, so I don't 
see any reason to stop at 2 GB.  Instead, it should loop up to the 
physical address size.

	-hpa
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