> > 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.
Virtual cpus are not running at 70% of real cpus :). Slowdown will happen if scheduler will run 2 processes on the same real cpu. And I read that there are patches for Linux kernel to fix that. Sooner rather than later they will appear in Linus kernel. Mindaugas ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
