* Re: /proc/mtrr & BIOS-provided RAM map
@ 2005-07-12 9:44 Mikael Pettersson
0 siblings, 0 replies; 2+ messages in thread
From: Mikael Pettersson @ 2005-07-12 9:44 UTC (permalink / raw)
To: linux-kernel, ssp
On Sat, 9 Jul 2005 01:00:54 -0700, Sheo Shanker Prasad wrote:
>(1) content of /proc/mtrr :
>
>reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
>reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
>reg02: base=0xc0000000 (3072MB), size= 128MB: write-back, count=1
>reg03: base=0xc8000000 (3200MB), size= 64MB: write-back, count=1
>reg04: base=0xd0000000 (3328MB), size= 256MB: write-combining, count=2
>
>(2) BIOS provided RAM map:
>
> BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
> BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
> BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
> BIOS-e820: 0000000000100000 - 00000000cbff0000 (usable)
> BIOS-e820: 00000000cbff0000 - 00000000cbfff000 (ACPI data)
> BIOS-e820: 00000000cbfff000 - 00000000cc000000 (ACPI NVS)
> BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved)
Your BIOS gives you "usable" memory up to 0xcbff0000-1,
but it set up the MTRRs to only cache up to 0xc8010000-1.
Thus the memory at 0xc8010000 to 0xcbff0000-1 will be slow as h*ll.
This is a BIOS problem. An upgrade (if available) may help.
Using mem=3264M should work around the MTRR issue. You've
apparently tried that, so whatever's causing your performance
variations must be something else.
/Mikael
^ permalink raw reply [flat|nested] 2+ messages in thread
* /proc/mtrr & BIOS-provided RAM map
@ 2005-07-09 8:00 Sheo Shanker Prasad
0 siblings, 0 replies; 2+ messages in thread
From: Sheo Shanker Prasad @ 2005-07-09 8:00 UTC (permalink / raw)
To: linux-kernel
I am having a horrible problem of wild and random variation in execution time
of of a benchmark test program from one fresh reboot to another fresh reboot
(and also from one try to another in any one reboot).
At the advice of a few colleagues at linux-kernel@vger.kernel.org and at
use-amd64@suse.com (who very kindly spared their valuable time to give me
some advice), I tried booting with mem=4000M, mem= 3264, mem=3000M and
mem=2000M (i.e, a value that is less than the actual RAM (4096M PC3200 in 4
dimms with 2 dimms on each CPU that is an Opteron 250 at 2.4 GHz) that are
under the control of SuSE 9.3 operating system.
None of the setting has helped. I continue to get the same wild and random
variation in the execution of the test program under identical conditions
(test program is the only program running, no Internet etc.).
Also, no matter what is set for xxxx in mem=xxxxM , the contents of
the /proc/mtrr & and the BIOS provide RAM map remain exactly the same
(although the dmesg shows the amount of memory change with the value of xxxx
in mem=xxxxM).
Is this normal? Does this show any BIOS problem? What these are telling me.
I will greatly appreciate any advice that any one may have for me on the above
questions. The following are the contents of /proc/mtrr and the BIOS provided
RAM map.
(1) content of /proc/mtrr :
reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
reg02: base=0xc0000000 (3072MB), size= 128MB: write-back, count=1
reg03: base=0xc8000000 (3200MB), size= 64MB: write-back, count=1
reg04: base=0xd0000000 (3328MB), size= 256MB: write-combining, count=2
(2) BIOS provided RAM map:
BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cbff0000 (usable)
BIOS-e820: 00000000cbff0000 - 00000000cbfff000 (ACPI data)
BIOS-e820: 00000000cbfff000 - 00000000cc000000 (ACPI NVS)
BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved)
Thanks for your help.
--
Best regards.
Sheo
(Sheo S. Prasad)
Creative Research Enterprises
6354 Camino del Lago
Pleasanton, CA 94566, USA
Voice Phone: (+1) 925 426-9341
Fax Phone: (+1) 925 426-9417
e-mail: ssp@CreativeResearch.org
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