[mdlug] Dual Core with Hyper Threading

[Jonathan Billings]

David Lane wrote:
> Looking in the PC stores I see a huge drop in cpu prices and the New
> Duo has Hyper threading so the operating systems "See" 4 CPU's. the
> last time I checked some Linux Distro's only allow 2.

If the linux distro is limiting CPUs, it's just with the kernel.  I know
I'm running a local variant of RHEL4 on several systems with two
dual-core CPUs in it, giving it 4 CPUs.  With hyperthreading turned on,
you'd see 8.

If you are curious if the CPU supports hyperthreading, check the 'flags'
line in /proc/cpuinfo.  If there is a 'ht' in there, it supports
hyperthreading.

There is a debate about whether running a system with hyperthreading
turned on actually improves performance.  In my experience, it depends
on the use of the system.  It'd probably improve performance as a
desktop system because the scheduler can spread the load across two
virtual CPUs.  If you're really pushing your CPU and memory to the
limit, you'll probably see worse performance with HT on than off.

-- 
Jonathan Billings <billings at negate.org>