Re: help tuning queries on large database

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At 07:28 PM 1/10/2006, Mark Lewis wrote:
Ron,

A few days back you mentioned:

> Upgrade your kernel to at least  2.6.12
> There's a known issue with earlier versions of the 2.6.x kernel and
> 64b CPUs like the Opteron.  See kernel.org for details.
>

I did some searching and couldn't find any obvious mention of this issue
(I gave up after searching through the first few hundred instances of
"64" in the 2.6.12 changelog).

Would you mind being a little more specific about which issue you're
talking about?  We're about to deploy some new 16GB RAM Opteron DB
servers and I'd like to check and make sure RH backported whatever the
fix was to their current RHEL4 kernel.
There are 3 issues I know about in general:
1= As Peter Royal noted on this list, pre 12 versions of 2.6.x have problems with RAM of >= 4GB.

2= Pre 12 versions on 2.6.x when running A64 or Xeon 64b SMP seem to be susceptible to "context switch storms".

3= Physical and memory IO is considerably improved in the later versions of 2.6.x compared to 2.6.11 or earlier.

Talk to a real Linux kernel guru (I am not) for details and specifics.
Ron




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