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

Karsten Desler
2004-12-07T18:38:52Z

Karsten Desler <kdesler@soohrt.org> wrote:
> > 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)

> > 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