Re: Dual Xeon + HW RAID question

SZUCS Gbor wrote:
> Alexandre,
>
> I missed your orig. post, but AFAIK multiprocessing kernels will handle HT
> CPUs as 2 CPUs each. Thus, our dual Xeon 2.4 is recognized as 4 Xeon 2.4
> CPUs.
>
> This way, I don't think HT would improve any single query (afaik no postgres
> process uses more than one cpu), but overall multi-query performance has to
> improve.

When you use hyperthreading, each virtual cpu runs at 70% of a full CPU,
so hyperthreading could be slower than non-hyperthreading. On a fully
loaded dual cpu system, you are looking at 2.8 cpu's (0.70 * 4), while
if it isn't loaded, you are looking at slowing down if you are only
using 1 or 2 cpu's.

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