On Fri, Jun 27, 2003, Brooks Davis wrote: > On Fri, Jun 27, 2003 at 06:39:12PM -0500, Glenn Johnson wrote: > > Thanks. I had read the smp manual page. I know _how_ to enable HTT; I > > was wondering whether I _should_ enable it. It seems the answer is that > > it is not beneficial in its current state because the scheduler does not > > yet differentiate between physical and logical processors. > > It's more complicated then that. For many users, it's true that HTT is > not useful due to the scheduling issues, but for some applications where > you keep all the CPUs busy, it does help. Somewhat suprisingly, > [EMAIL PROTECTED] performs better with HTT enabled then without. The individual > workunits take longer to process, but the overall throughput is better > (4 workunits every 6hrs instead of 2 workunits every 4hrs).
Hyperthreading will generally give you better thoughput because you get better utilization of the hardware; when one functional unit would normally be idle due to a pipeline bubble, the other logical CPU may be able to provide work for it. On the other hand, as you observe, latency is worse. In particular, if you're running a web browser on one processor, it's competing for resources with your [EMAIL PROTECTED] client on the other processor, even though the [EMAIL PROTECTED] client is niced. _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "[EMAIL PROTECTED]"
