Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?

On Tue, Feb 20, 2007 at 05:27:14PM +0100, bert hubert (bert.hubert@netherlabs.nl) wrote:

I've done so, with some interesting results. Source on
http://ds9a.nl/tmp/recvtimings.c - be careful to adjust the '3000' divider
to your CPU frequency if you care about absolute numbers!

These are two groups, each consisting of 10 consecutive nonblocking UDP
recvfroms, with 10 packets preloaded. Reported is the number of microseconds
per recvfrom call which yielded a packet:

$ ./recvtimings
4.142333

It can be recvfrom only problem - syscall overhead on my p4 (core duo,
debian testing) is bout 300 usec - to test I ran 
read('dev/zero', &data, 0)
in a loop.

Could you try to hack recvfrom() for your socket to always copy some
empty buffer and check the results without waiting for packet?

If you are not hurry I can test it myself tomorrow.

-- 
	Evgeniy Polyakov