[Beowulf] Optimal BIOS settings for Tyan K8SRE

stephen mulcahy smulcahy at aplpi.com
Mon Sep 4 09:27:40 EDT 2006


Hi Bruce,

Do you have any idea what the performance impact from enabling scrubbing
is on your systems? did you do any before/after benchmarking?

Thanks,

-stephen

Bruce Allen wrote:
> On Sun, 3 Sep 2006, Mark Hahn wrote:
> 
>>>     ECC Features
>>>         ECC    Enabled
>>>         ECC Scrub Redirection    Enabled
>>>         Dram ECC Scrub CTL    Disabled
>>>         Chip-Kill    Disabled
>>>         DCACHE ECC Scrub CTL    Disabled
>>>         L2 ECC Scrub CTL    Disabled
> 
> You can find our systems BIOS/ECC/Scrub settings here:
> http://www.lsc-group.phys.uwm.edu/beowulf/nemo/construction/BIOS/bios_settings.txt
> 
> Our systems are Supermicro H8SSL-i motherboards, with a
> Serverworks/Broadcom HT1000 chipset and a single Opteron 175 (dual core,
> 2.2 GHz).
> 
> The ECC part is:
>  DRAM ECC Enable = Enabled
>  MCA DRAM ECC Logging = Enabled
>  DRAM Scrub Redirect = Enabled
>  DRAM BG Scrub = 2.62ms
>  L2 Cache BG Scrub = 84.00ms
>  Data Cache BG Scrub = 84.00ms
> 
> Scrubbing is done one cache line (64) bytes at a time.  Thus with 2GB of
> memory and DRAM background scrub interval of 2.62ms we will scrub the
> entire memory in approximately:
> 
> 2 GB/64 Bytes * 2.62 ms = 2^31 / 2^6 * 2.62 ms = 87912 secs
> 
> So our choices correspond to one complete scrub of DRAM per day.  Our
> settings scrub the L2 cache more often: about once every half hour. 
> Just modify the calculation above, using 1MB instead of 2GB, and 84 ms
> instead of 2.62 ms.  One finds that the L2 cache is scrubbed about once
> every 1376 seconds (every 23 minutes).
> 
> Cheers,
>     Bruce

-- 
Stephen Mulcahy, Applepie Solutions Ltd, Innovation in Business Center,
   GMIT, Dublin Rd, Galway, Ireland.      mailto:smulcahy at aplpi.com
  mobile:+353.87.2930252  office:+353.91.751262  http://www.aplpi.com
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