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

* Willy Tarreau wrote:

On Tue, Dec 07, 2004 at 12:21:39PM +0100, Karsten Desler wrote:
 

quoted

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).

Have you checked the interrupts rate ? I had an e1000 eating many CPU cycles
because it would generate 50000 interrupts/s. Passing the module
InterruptThrottleRate=5000 definitely calmed it down, and more than doubled
the data rate.

I was running mit ITR=3000, but as a test to see if NAPI works, I
disabled ITR on eth0 bringing the int/s rate up to 50k.
Is that normal? I always though NAPI was supposed to kick in way earlier.
Anyways, I'm going to try different ITR settings to see if they make any
difference.

Cheers,
 Karsten