[Tfug] Dual cores and hyperthreading

[Michael Salivar]

When dealing with SMT (hyperthreading) or multicore chips there are a
couple new scheduler options in the kernel as well.  I believe they're
completely optional, but they should help tune performance a bit.

On Sat, 19 Aug 2006 14:39:27 -0700
John Gruenenfelder <johng at as.arizona.edu> wrote:

> Hey all,
> 
> I've got a hardware question about dual cores and hyperthreading.  My new
> laptop has a core duo chip inside.  To utilize both cores, all you need is a
> SMP kernel.  Easy enough.
> 
> But, the core duo is also based on the Pentium 4m which supports
> hyperthreading.  This is confirmed by running cpuid:
> 
> ---------
> Extended brand string: "Genuine Intel(R) CPU           T2400  @ 1.83GHz"
> CLFLUSH instruction cache line size: 8
> Initial APIC ID: 1
> Hyper threading siblings: 2
> 
> Feature flags bfe9fbff:
> ...
> SS     Self Snoop
> HT     Hyper Threading
> TM     Thermal monitor
> ...
> ---------
> 
> Is is possible to take advantage of this as well?  My understanding is that
> hyperthreading is 2 virtual CPUs in a single core and so it should be separate
> from the hardware which enables two physical cores thus making it possible to
> use both at the same time.
> 
> Last time I used a HT capable machine in Linux (a while ago), I didn't need
> anything extra other than an SMP kernel.
> 
> Am I confused about the situation?  Maybe I need additional support from
> elsewhere in the machine like the BIOS (I already looked in there)?
> 
>