Intel's Hyper threading is simply a marketing feature. The only technology
involved is adding a second set of registers to a single core. Hence you now
have 1 compute engine attempting to execute 2 instructions streams. Both
instruction streams share the same cache, memory bus, execute engine leading
to increased contention, not increased performance. Hence you get 1/2 the
cpu power each. The "context switching" is done at the chip level, not the
OS level. hence the OS can not benefit from it. The only way hyperthreading
could provide any benefit would be if your OS was crafty enough to allocate
a totoally compute bound thread (no memory/disk access) with a non compute
bound thread. We have disabled hyperthreading in BIOS and have seen huge
performance increases in our compute bound activitites (20 seconds goes down
to 15 seconds).
"Tanel Poder" <tanel@@peldik.com> wrote in message
news:3f1d36ec$1_1_at_news.estpak.ee...
> Hi!
>
> At least Redhat Advanced Server 2.1 sees hyperthreaded processors, that a
> 4way SMP box is actually seen as 8way.
> But I wouldn't recommend using Oracle's parallel featres with 1 CPU
machine
> with hyperthreading, because parallel execution needs quite much
> coordinating between slaves etc so you can make your processes even slower
> than with serial execution.
>
> Hyperthreading doesn't make 2 CPUs of one, it just allows us to use CPU
> strength better with (quite a) few tricks.
>
> Tanel.
>
> "kshathrya" <kshathrya_at_hotmail.com> wrote in message
> news:StBSa.107361$ye4.78464_at_sccrnsc01...
> > hi all,
> > does red hat linux 9 support hyperthreaded p4 systems?
> > if i install oracle 9i on a rehat linux 9 hyperthreaded system, can i
see
> > that as 2 virtual processor from oracle's perspective?
> > can i use oraclel's parallel features with these virtual processor?
> >
> > tnx,
> > ks
> >
> >
>
>
Received on Tue Jul 22 2003 - 08:31:56 CDT
