[netperf-talk] CPU Utilization Issues

[Andrew Gallatin]

Rick Jones wrote:

> Anyhow, latency, especially small packet latency, is dominated by 
> path-length vs CPU "oomph" and the interrupt coalescing decisions made 
> by the NIC/driver.  An older writeup at:

One thing which some people may find surprising is that at least on
recent Intel Nehalem based servers, I've seen roughly a factor of
2 improvement in UDP_RR numbers simply by disabling all powersaving
in the BIOS (over and above disabling interrupt coalescing on the NIC).
I'm guessing there are many microseconds of latency to wake up a
slumbering core to handle a NIC interrupt and/or SMP IPI.

Drew