linux-kernel - Re: [PATCH 2/2] x86: mtrr_cleanup try gran

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Message-ID: <20081003074246.GE4950@elte.hu>
Date:	Fri, 3 Oct 2008 09:42:46 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"J.A. Magallón" <jamagallon@....com>,
	Linux-Kernel <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/2] x86: mtrr_cleanup try gran_size to less than 1M


* H. Peter Anvin <hpa@...or.com> wrote:

> Ingo Molnar wrote:
>> * J.A. Magallón <jamagallon@....com> wrote:
>>
>>> Also, on a 64 bit box with 4Gb, it gives this:
>>>
>>> cicely:~# cat /proc/mtrr
>>> reg00: base=0x00000000 (   0MB), size=4096MB: write-back, count=1
>>> reg01: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
>>> reg02: base=0x140000000 (5120MB), size= 512MB: write-back, count=1
>>> reg03: base=0x160000000 (5632MB), size= 256MB: write-back, count=1
>>> reg04: base=0x80000000 (2048MB), size=2048MB: uncachable, count=1
>>>
>>> Patch below cleans up formatting, with space for big bases and sizes (64 Gb).
>>
>> applied to tip/x86/mtrr, thanks!
>>
>>> +++ arch/x86/kernel/cpu/mtrr/if.c     2008-10-03 00:22:34.000000000 +0200
>>> @@ -16,7 +16,7 @@
>>>  static const char *const mtrr_strings[MTRR_NUM_TYPES] =
>>>  {
>>>      "uncachable",               /* 0 */
>>> -    "write-combining",          /* 1 */
>>> +    "write-combine",            /* 1 */
>>
>> hm, maybe this bit could confuse versions of Xorg that modifies  
>> /proc/mtrr - i.e. this could be part of the ABI towards user-space.  
>> We'll see.
>>
>
> This *IS* part of the ABI toward userspace, although I think Xorg uses 
> the ioctl() interface.

yeah, but aspects of the ABI that applications do not rely on can 
generally be changed. OTOH, i've undone this aspect of the patch - 
/proc/mtrr is a legacy interface and changes to it are unnecessary. I 
kept the boot printout cleanups.

	Ingo
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