>Hyper threading. It's usually not recommended to enable it on
>PostgreSQL servers. On most servers, you can disable it directly in
>the BIOS.

Maybe for specific usage scenarios, but that's generally not been my experience 
with relatively recent versions of PG. We ran some tests with pgbench, and 
averaged 10% or more performance improvement. Now, I agree pgbench isn't the 
most realistic performance, but we did notice a slight improvement in our 
application performance too.

Also, here's some benchmarks that were posted earlier by the folks at 
tweakers.net also showing hyperthreading to be faster:

http://tweakers.net/reviews/646/10

I'm not sure if it's dependent on OS- our tests were on BSD 5.x and PG 7.4 and 
8.0/8.1 and were several months ago, so I don't remember many more specifics 
than that. 

So, not saying it's a best practice one way or another, but this is pretty easy 
to test and you should definitely try it out both ways for your workload.

- Bucky 


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