Re: Scaling noise

Alan Cox
2003-09-08T13:41:40Z

On Sad, 2003-09-06 at 16:08, Pavel Machek wrote:
> Hi!
>
> > Maybe this is a better way to get my point across. Think about more CPUs
> > on the same memory subsystem. I've been trying to make this scaling point
>
> The point of hyperthreading is that more virtual CPUs on same memory
> subsystem can actually help stuff.

Its a way of exposing asynchronicity keeping the old instruction set.
Its trying to make better use of the bandwidth available by having
something else to schedule into stalls. Thats why HT is really good for
code which is full of polling I/O, badly coded memory accesses but is
worthless on perfectly tuned hand coded stuff which doesnt stall.

Its great feature is that HT gets *more* not less useful as the CPU gets
faster..