Re: no more MTRRs available ?

William Lee Irwin III
2003-01-29T17:53:38Z

On Wed, Jan 29, 2003 at 09:20:01AM -0800, William Lee Irwin III wrote:
>> Looks better than what I'm getting on 2.5.59:
>> curly:~# cat /proc/mtrr
>> reg00: base=0xc0000000 (49152MB), size=16384MB: uncachable, count=1
>> reg01: base=0x00000000 ( 0MB), size=524288MB: write-back, count=1
>> reg02: base=0x800000000 (524288MB), size=262144MB: write-back, count=1
>> Yes, this is standard ia32 (P-III/Coppermine cpus), and hence the
>> numbers here are utter garbage.

On Wed, Jan 29, 2003 at 05:48:42PM +0000, Dave Jones wrote:
> Bizarre. The size field isn't being shifted, and your base is somewhere
> off in 64bit land.
> See Andi's "RED-PEN" comments in various parts of arch/i386/kernel/cpu/mtrr/
> They need fixing at some point, and could be the cause of your problems.

OTOH since 0-512GB are in there this explains why the (massive) perf.
decrease only happens sometimes. The MTRR corruption issues are only
visible with 48GB atm. I haven't been focusing on MTRR's but I may
arrange to trace the codepaths etc. in the eventual future to find
where the bits are going bad esp. as benchmark time approaches.

-- wli