HTT on Atom (Was: FreeBSD 8.0 and Atheros AzureWave wireless chipset)

[Manolis Kiagias]

Brett Glass wrote:
> At 04:33 PM 11/26/2009, Manolis Kiagias wrote:
>
>> Though it seems hyperthreading is improved on the Atom and there is no
>> penalty for leaving it on.
>
> Is there really no penalty? With HZ=1000 there are double the clock
> interrupts to be serviced at least. And as I understand it the Atom
> has less redundant hardware, so there are less likely to be unused
> resources available to the second thread. I am seeing substantially
> faster compiles with the SMP option commented out of the kernel.
>
> --Brett
>
My tests involved building a custom kernel - I never tried without SMP,
just without hyperthreading and there was no appreciable difference.
Using -j3 in make kernel, the kernel is built in just about 40 minutes.
Without -j same procedure lasts 55 minutes. (I am using an Atom 330
which is dual core)

On a Pentium 4 with HTT, -j actually results in a somewhat slower build.