Messages in this thread | | | Date | Tue, 7 Dec 2004 12:21:39 +0100 | From | Karsten Desler <> | Subject | Re: _High_ CPU usage while routing (mostly) small UDP packets |
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* P@draigBrady.com wrote: > Karsten Desler wrote: > >* David S. Miller wrote: > > > >>It's spending nearly half of it's time in iptables. > >>Try to consolidate your rules if possible. This is the > >>part of netfilter that really doesn't scale well at all. > >> > > > >Removing the iptables rules helps reducing the load a little, but the > >majority of time is still spent somewhere else. > > Well with NAPI it can be hard to tell CPU usage. > You may need to use something like cyclesoak to get > a true idea of CPU left.
Thanks, I'll look into it.
> 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.
> 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).
> Anyway attached is a small patch that I used to make the e1000 > "own" the packet buffers, and hence it does not alloc/free > per packet at all. Now this has only been tested in one > configuration where I was just sniffing the packets, so > definitely YMMV.
Thanks, I'll give it a spin.
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