severe performance degradation on serverworks with high mem

severe performance degradation on serverworks with high mem

[Brian C. Thomas]

Hi

I have a Supermicro S2QR6 board, which has the "Serverworks serverset
III HE" chipset.  (Also, i have 8GB RAM, 4 Xeon P3 700MHz processors,
and an Adaptec Ultra160 SCSI system - aix7xxx, built onto the 
motherboard)

In all the 2.4.x series kernels (even up to 2.4.12-ac3 or
2.4.13-pre4), as soon as the high memory, 64GB option is enabled, the
server slows down to a crawl, with no load showing.  (A "crawl"
example is a kernel recompile time going from ~5 min to >2 hr!)

I have tried numerous kernel config options, removing scsi support,
networking, and have narrowed the problem down to the serverworks
chipset- on a SC440NX mb, also with 8GB and everything else in the
system, all the new kernels work with no slowdown.

I've tried...
kernels: 2.4.1, 2.4.3, 2.4.5, 2.4.7-ac9, 2.4.9, 2.4.12 (-pre4, -ac3)
with and w/o mtrr support kernel config

Any ideas?

Thanks,

BCT

____________________________
Brian C. Thomas
bcthomas@nature.berkeley.edu

Re: severe performance degradation on serverworks with high mem

[Brian C. Thomas]

Hi

I don't know if this helps, but I seem to have stumbled onto a
possible "fix" for this...

With 64GB high memory enabled in kernel 2.4.12-ac3, and mtrr turned
on, I was able to see all 8GB RAM on my machine by using the old
'append="mem=8000M"' command in my lilo.conf file... AND WITH NO LOSS
OF PERFORMANCE!

Does that help anyone with defining where this problem is coming from?

BCT

____________________________
Brian C. Thomas
bcthomas@nature.berkeley.edu

On Thu, Oct 18, 2001 at 12:57:15PM -0700, Brian C. Thomas wrote:
> Hi
> 
> I have a Supermicro S2QR6 board, which has the "Serverworks serverset
> III HE" chipset.  (Also, i have 8GB RAM, 4 Xeon P3 700MHz processors,
> and an Adaptec Ultra160 SCSI system - aix7xxx, built onto the 
> motherboard)
> 
> In all the 2.4.x series kernels (even up to 2.4.12-ac3 or
> 2.4.13-pre4), as soon as the high memory, 64GB option is enabled, the
> server slows down to a crawl, with no load showing.  (A "crawl"
> example is a kernel recompile time going from ~5 min to >2 hr!)
> 
> I have tried numerous kernel config options, removing scsi support,
> networking, and have narrowed the problem down to the serverworks
> chipset- on a SC440NX mb, also with 8GB and everything else in the
> system, all the new kernels work with no slowdown.
> 
> I've tried...
> kernels: 2.4.1, 2.4.3, 2.4.5, 2.4.7-ac9, 2.4.9, 2.4.12 (-pre4, -ac3)
> with and w/o mtrr support kernel config
> 
> Any ideas?
> 
> Thanks,
> 
> BCT
> 
> ____________________________
> Brian C. Thomas
> bcthomas@nature.berkeley.edu
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Re: severe performance degradation on serverworks with high mem

[Mike Fedyk]

On Thu, Oct 18, 2001 at 02:45:05PM -0700, Brian C. Thomas wrote:
> Hi
> 
> I don't know if this helps, but I seem to have stumbled onto a
> possible "fix" for this...
> 
> With 64GB high memory enabled in kernel 2.4.12-ac3, and mtrr turned
> on, I was able to see all 8GB RAM on my machine by using the old
> 'append="mem=8000M"' command in my lilo.conf file... AND WITH NO LOSS
> OF PERFORMANCE!
> 
> Does that help anyone with defining where this problem is coming from?
> 

The real question is how to reproduce the > 2hr kernel compiles.

Are there any certain steps that would reliably create the problem, and if
so what are they?

Re: severe performance degradation on serverworks with high mem

[Eric W. Biederman]

"Brian C. Thomas" <bcthomas@nature.Berkeley.edu> writes:

> Hi
> 
> I don't know if this helps, but I seem to have stumbled onto a
> possible "fix" for this...
> 
> With 64GB high memory enabled in kernel 2.4.12-ac3, and mtrr turned
> on, I was able to see all 8GB RAM on my machine by using the old
> 'append="mem=8000M"' command in my lilo.conf file... AND WITH NO LOSS
> OF PERFORMANCE!
> 
> Does that help anyone with defining where this problem is coming from?

cat /proc/mtrr and see what the mtrrs look like.  It feels like there you
have a spot of RAM the BIOS doesn't cover with mtrrs.

Eric