Re: Dual Xeon + HW RAID question

SZUCS G�bor 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.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073