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

jamal wrote:

On Tue, 2004-12-07 at 07:50, Karsten Desler wrote:

quoted

Currently I'm having problems capturing packets with tcpdump (lots of
"packets dropped by kernel") which indicates to me that there's
genuinely not much (enough) idle time sitting around.

Ah, more hints. So you are not trying to forward - rather just packet
capturing?
Are you using a tcpdump patched with mmaped packet socket?

The 230-240Kpps you are reporting as a capture dont seem as unreasonable
as i thought then. Neither would the CPU use.

Yes this is vital Karsten, otherwise tcpdump
will do 2 syscalls per packet, which is the
bottleneck in my experience.

You may want to try a simpler capture program that
uses the kernel PACKET_MMAP feature directly:
http://www.scaramanga.co.uk/code-fu/lincap.c

-- 
Pádraig Brady - http://www.pixelbeat.org
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