Re: _High_ CPU usage while routing (mostly) small UDP packets

Karsten Desler [off-list ref] wrote:

quoted

Also have a look at http://www.hipac.org/ as netfilter
has silly scalability properties.

I did before, but I read on Harald Weltes' weblog that 2.4 gives
slightly worse pps results than 2.6, and since the cpu usage is as high
as it is, I didn't want to take any more performance hits.
I'll try to see what performance impact the netfilter rules have during
peak load.

using 2 CPUs
System load: 61.4% || Free:  51.0%(0)  26.3%(1)
System load: 59.6% || Free:  53.6%(0)  27.3%(1)
System load: 59.6% || Free:  53.6%(0)  27.3%(1)
System load: 59.7% || Free:  53.6%(0)  27.0%(1)
System load: 60.3% || Free:  53.0%(0)  26.4%(1)
System load: 51.9% || Free:  60.4%(0)  35.8%(1) <- iptables -F
System load: 50.1% || Free:  62.1%(0)  37.7%(1)
System load: 50.1% || Free:  62.0%(0)  37.8%(1)
System load: 50.6% || Free:  61.6%(0)  37.2%(1)
System load: 50.5% || Free:  61.7%(0)  37.3%(1)

quoted

I also notice that a lot of time is spent allocating
and freeing the packet buffers (and possible hidden
time due to cache misses due to allocating on one
CPU and freeing on another?).
How many [RT]xDescriptors do you have configured by the way?

256. I increased them to 1024 shortly after the profiling run, but
didn't notice any change in the cpu usage (will try again with cyclesoak).

Again, no effect.

Cheers,
 Karsten