Subject: Re: Netperf TCP_RR(loopback) 10% regression in 2.6.24-rc6, comparing with 2.6.22

From: "Zhang, Yanmin" <[email-masked]>
Date: Wed, 23 Jan 2008 08:42:24 +0800

On Tue, 2008-01-22 at 10:36 -0800, Rick Jones wrote:
> When parsing the -P option in scan_socket_args() of src/nettest_bsd.c, 
> netperf is using "break_args()" from src/netsh.c which indeed if the 
> command line says "-P 12345" will set both the local and remote port 
> numbers to 12345.  If instead you were to say "-P 12345,"  it will use 
> 12345 only for the netperf side.  If you say "-P ,12345" it will use 
> 12345 only for the netserver side.  To set both sides at once to 
> different values it would be "-P 12345,54321"
> 
> In theory, send_udp_rr() in src/nettest_bsd.c (or I suppose 
> scan_socket_args() could have more code added to it to check for a UDP 
> test over loopback, but probably needs to be a check for any local IP, 
> and unless this becomes something bigger than "Doctor! Doctor! It hurts 
> when I do this!" :) I'm inclined to leave it as caveat benchmarker and 
> perhaps some additional text in the manual.
I will instrument kernel to see if kernel does work like it is expected.

When an issue is found, we shouldn't escape by saying it's nothing to do
with me.

-yanmin