8Mb file should be enough.
At least, I do see real difference between the first and subsequent
runs with 32MB file and 512M machine. You do not and this is funny.
> I think the L2 cache on these machine is 512KB. So something slightly
> larger (600KB)?
>2*L2 cache. Otherwise it is not invalidated.
> How Large? 170M currently.
Seems, your first experiment was 16M. It was reasonable.
I have no idea why you did not see differences between runs,
it is simply impossible.
> tput: 68MB/sec (compare to 86MB/sec)
Sorry? But what did you measure earlier? 8)
> So i would say that CPU utilization has improved incredibly, but
> throughput has gone down.
I have no idea, throughput grows here on similar hardware.
And by the way, numbers are pretty similar, but inverted. 8)