What does hyperthreading actually buy?

There has been some discussion about the benefits of hyperthreading, or
lack thereof. Here's a link to information on a single web server which
supports 20k connections using a pair of slow Xeons. Turning on HT gave
a 37% boost in performance, measured as tps or pages served per sec.

http://kb.pert.switch.ch/cgi-bin/twi.../ApacheScaling

I typically see 20-30% for big compiles, on a single CPU with HT, but
this shows that there's a gain even if you have dual core.

--
bill davidsen
SBC/Prodigy Yorktown Heights NY data center
http://newsgroups.news.prodigy.com

"Bill Davidsen" wrote in message
...
There has been some discussion about the benefits of hyperthreading, or
lack thereof. Here's a link to information on a single web server which
supports 20k connections using a pair of slow Xeons. Turning on HT gave
a 37% boost in performance, measured as tps or pages served per sec.

http://kb.pert.switch.ch/cgi-bin/twi.../ApacheScaling

I typically see 20-30% for big compiles, on a single CPU with HT, but
this shows that there's a gain even if you have dual core.


Their first version of it rarely gave me over a 10% improvement, but since I
have consistently seen a 25% improvement and often more. I actually like
the technology now. The new CPUs won't have it since they are more
efficient, but it will have helped push the transition to multithreaded
program as much as anything.