linux-kernel - Re: MTRR allocation failure

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Message-ID: <CAE9FiQX5ZL5LbQtVfbKCvbJoPvkOhvmCtsvEXAJZU1+48R9_WQ@mail.gmail.com>
Date:	Fri, 9 Sep 2011 19:47:38 -0700
From:	Yinghai Lu <yinghai.lu@...cle.com>
To:	Parag Warudkar <parag.lkml@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: MTRR allocation failure

On Fri, Sep 9, 2011 at 5:54 PM, Parag Warudkar <parag.lkml@...il.com> wrote:
>
> I had the below messages in log and not other noticeable slowness.
>
> mtrr: no more MTRRs available
> [drm] MTRR allocation failed.  Graphics performance may suffer.
>
> I was able to pass mtrr_gran_size=128M enable_mtrr_cleanup to kernel
> command line and those messages went away but I lost 143MB of RAM.
>
> I recently did a BIOS upgrade to resolve some other unrelated issues and
> now even with the above command line options the MTRR allocaiton failure
> is back but I don't have any lost RAM - this time too without any
> notieceable slowness. I tried various options for mtrr_gran_size and
> mtrr_spare_reg_nr with no change.
>
> cat /proc/mtrr :
>
> reg00: base=0x0ffc00000 ( 4092MB), size=    4MB, count=1: write-protect
> reg01: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
> reg02: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
> reg03: base=0x0c0000000 ( 3072MB), size=  512MB, count=1: write-back
> reg04: base=0x0dc000000 ( 3520MB), size=   64MB, count=1: uncachable
> reg05: base=0x0db000000 ( 3504MB), size=   16MB, count=1: uncachable
> reg06: base=0x100000000 ( 4096MB), size= 4096MB, count=1: write-back
> reg07: base=0x200000000 ( 8192MB), size=  512MB, count=1: write-back
> reg08: base=0x21f000000 ( 8688MB), size=   16MB, count=1: uncachable
> reg09: base=0x21e800000 ( 8680MB), size=    8MB, count=1: uncachable
>
> Sounds like some uncachable entries can be merged? I disabled #08, 09, 04
> and 05 with no immediate side effects.
>
> Is there any other option combo I can try to have some free entries for
> X/drm?

your BIOS create one new WP entry. so mtrr sanitizer is not triggered...

Maybe you can just delete first entry before you load drm?

Yinghai
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