Re: Opteron box and 4Gb memory

From: J.A. Magallón
Date: Mon Nov 05 2007 - 13:45:42 EST

On Mon, 5 Nov 2007 13:10:46 -0500, lsorense@xxxxxxxxxxxxxxxxxxx (Lennart Sorensen) wrote:

> On Mon, Nov 05, 2007 at 12:18:47AM +0100, J.A. Magall?n wrote:
> > Well, I was able to get about 3 Gb with MTRR=discrete in the BIOS,
> > but I'm still in the process to find the 'software hole' option to get
> > the rest of the 4Gb...
> >
> > But now another (perhaps related) question has arised...
> > I like all those 5-line progams to test system performance...;).
> > I just wrote a simple program that sums/muls int/float vectors with
> > scalar/sse operations. And my opteron box looks terribly slow.
> >
> > This is my MacPro, Xeon 5130:
> >
> > belly:~/bn> bn
> > proc: 4 x MacPro1,1 @ 2000 MHz
> > ram: 2048 Mb
> > os: unx, Darwin, 9.0.0
> > cc: gcc-4.0.1
> > vector size : 8 x 1024 x 1024
> > allocation: 0.01 ms
> > int scl add: .......... 36.78 ms, 228.07 Mips | 114.03 Mips /GHz
> > int scl mul: .......... 34.30 ms, 244.60 Mips | 122.30 Mips /GHz
> > flt scl add: .......... 34.28 ms, 244.73 Mflops | 122.37 Mflops/GHz
> > flt vec add: .......... 7.89 ms, 1063.15 Mflops | 531.58 Mflops/GHz
> > flt scl mul: .......... 34.20 ms, 245.28 Mflops | 122.64 Mflops/GHz
> > flt vec mul: .......... 7.90 ms, 1061.77 Mflops | 530.89 Mflops/GHz
> > total: 3322.19 ms
> >
> > This is a normal (I think) opteron box (Opteron 846):
> >
> > selene:~/bn> g
> > proc: 4 x x86_64 @ 2004 MHz
> > ram: 3496 Mb
> > os: unx, Linux, 2.6.9-42.0.10.ELsmp
> > cc: gcc-4.0.2
> > vector size : 8 x 1024 x 1024
> > allocation: 0.05 ms
> > int scl add: .......... 45.98 ms, 182.42 Mips | 91.03 Mips /GHz
> > int scl mul: .......... 44.31 ms, 189.30 Mips | 94.46 Mips /GHz
> > flt scl add: .......... 44.52 ms, 188.41 Mflops | 94.02 Mflops/GHz
> > flt vec add: .......... 10.03 ms, 836.70 Mflops | 417.52 Mflops/GHz
> > flt scl mul: .......... 43.32 ms, 193.63 Mflops | 96.62 Mflops/GHz
> > flt vec mul: .......... 10.02 ms, 836.98 Mflops | 417.65 Mflops/GHz
> > total: 4705.07 ms
> >
> > And this is my opteron (Opteron 275)
> >
> > cicely:~/bn> g
> > proc: 4 x x86_64 @ 2200 MHz
> > ram: 2914 Mb
> > os: unx, Linux, 2.6.23.1-desktop-1mdv
> > cc: gcc-4.0.2
> > vector size : 8 x 1024 x 1024
> > allocation: 0.03 ms
> > int scl add: .......... 87.67 ms, 95.68 Mips | 43.49 Mips /GHz
> > int scl mul: .......... 85.48 ms, 98.13 Mips | 44.61 Mips /GHz
> > flt scl add: .......... 85.90 ms, 97.66 Mflops | 44.39 Mflops/GHz
> > flt vec add: .......... 19.51 ms, 429.96 Mflops | 195.44 Mflops/GHz
> > flt scl mul: .......... 85.86 ms, 97.70 Mflops | 44.41 Mflops/GHz
> > flt vec mul: .......... 19.50 ms, 430.11 Mflops | 195.50 Mflops/GHz
> > total: 6334.96 ms
> >
> > As I read in AMD site, the only difference that matters in models is
> > the xx5 vx xx6, related to fequency, but the processors should be just
> > the same.
> >
> > As this only does intensive memory/fp operations, I'm not going to blame
> > gcc nor kernel versions here (I have compared gcc 3.4, 4.0, 4.1, and 4.2
> > on one of the boxes and results are very similar, the code is really
> > stupid and not very suitable for compiler smartness...).
> > I suspect it is a memory problem. It can be hardware or caused by
> > incorrect BIOS/kernel-mtrr setup:
> >
> > selene:~> cat /proc/mtrr
> > reg00: base=0x00000000 ( 0MB), size=16384MB: write-back, count=1
> > reg01: base=0xf0000000 (3840MB), size= 256MB: uncachable, count=1
> >
> > cicely:~> cat /proc/mtrr
> > reg00: base=0x00000000 ( 0MB), size=2048MB: write-back, count=1
> > reg01: base=0x80000000 (2048MB), size= 512MB: write-back, count=1
> > reg02: base=0xa0000000 (2560MB), size= 256MB: write-back, count=1
> > reg03: base=0xb0000000 (2816MB), size= 128MB: write-back, count=1
> > reg04: base=0xb8000000 (2944MB), size= 16MB: write-back, count=1
> >
> >
> > Any idea on what can be going on here ? I have asked the 'good opteron'
> > admin info about the mobo an memory of the box.
> >
> > Any help will be _very_ appreciated.
>
> Well what revisions are the two opterons? Is one running dual channel
> memory while the other isn't perhaps? What speed and type is the ram on
> the two opterons?
>

Well, problem solved...

I'm going to kill all pc assemblers in the world... Someone should teach them
to learn mauals before assembling anything but a power chord.

The memory was not paired, so the motherboard was not interleaving the access.
With no inter-node but with inter-module interleaving, and a couple 1Gb sticks
for each processor now I get something like:

cicely:~/bn> bn
name: cicely.cps.unizar.es
arch: x86-64
proc: 4 x x86_64 @ 2200 MHz
ram: 3555 Mb
os: unx, Linux, 2.6.23.1-desktop-1mdv
cc: gcc-4.3.0
vector size : 8 x 1024 x 1024
allocation: 0.02 ms
int scl add: .......... 60.56 ms, 138.52 Mips | 62.96 Mips /GHz
int scl mul: .......... 59.34 ms, 141.36 Mips | 64.26 Mips /GHz
flt scl add: .......... 59.01 ms, 142.16 Mflops | 64.62 Mflops/GHz
flt vec add: .......... 14.79 ms, 567.06 Mflops | 257.75 Mflops/GHz
flt scl mul: .......... 59.02 ms, 142.12 Mflops | 64.60 Mflops/GHz
flt vec mul: .......... 14.82 ms, 566.19 Mflops | 257.36 Mflops/GHz
total: 5019.86 ms

Much better, but not like the other opteron box.

My processors are higher than Rev E0, because the BIOS does not let me choose
the 'software' hole. If I activate the 'hardware hole', I see al the memory
I can:

cicely:~/bn> free
total used free shared buffers cached
Mem: 3640628 214496 3426132 0 21240 84184
-/+ buffers/cache: 109072 3531556
Swap: 4200988 0 4200988

3.64 Gb. The rest is eaten by the graphics card, as I could read in the
AMD site. Don't know if mem=4096 to boot the kernel would help, even if it
is possible (don't think so, as it looks like a BIOS mis-feature).
The ram is DDR 400.

Anyways, can I trust what dmidecode says ? I installed the ram as the board
manual said in banks 1A+1B (not 2A+2B) for each processor, but this program
says this:

BANK0 64Mb BANK4 64Mb
BANK1 64Mb BANK5 64Mb
BANK2 1024Mb BANK6 1024Mb
BANK3 1024Mb BANK7 1024Mb

I would always have thought that BANK0 would be slot 1A in first processor,
but it looks like not...
And where do the 64 Mb blocks come from ?

Really strange...

--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2008.1 (Cooker) for i586
Linux 2.6.23-jam01 (gcc 4.2.2 20070909 (4.2.2-0.RC.1mdv2008.0)) SMP PREEMPT
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
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