🚀 go-pugleaf

In aus.computers.linux CyBorg_0091 <coldascoldx@netscape.net> wrote:
> I was waiting for Hyperthreading and Linux

Why wait?  Linux had it first...

> Some XP kids are going to seriously ponder the meaning of life if they read
> your description.

Except that his description is _wrong_.

> Whats the point of hyperthreading if you can't see it!

The Linux kernel makes the 2 hyperthreaded "processors" appear as
separate processors.  If you had a box with an SMP motherboard
with 2 HT processors, you'd have 4 virtual processors and that's
what you'd see under linux.  HT _is_ virtual SMP and is treated
as SMP by the kernel.  If you don't use an SMP kernel, you won't
enable HT.

In kernel 2.4, the 4 virtual processors would be essentially
indistinguishable and a lightly loaded system could easily load
the first 2 (ie the ones in one chip) with 2 heavy processes
while the other 2 virtual processors (the other chip) are still
just idling over.

The 2.6 kernel is intended to provide "processor affinity", in
which the kernel will know which virtual processors are in which
processor and be able to intelligently allocate processes to
processors in the most efficient possible manner.  This includes
such things as putting processes that will use a lot of the same
shared memory on the virtual processors within the same physical
chip to maximise cache hits, putting an even amount of load on
the separate physical processors in spite of low loads on 2nd
hyperthreaded virtual processor of the first chip, etc...

-- 
Athol
<http://cust.idl.com.au/athol>
Linux Registered User # 254000
I'm a Libran Engineer. I don't argue, I discuss.