voluntary-preempt-2.6.8.1-P1 seems to lose UDP messages.

["P.O. Gaillard" <pierre-olivier.gaillard@fr.thalesgroup.com>]

Hello,

I have a real-time application that transmits 20 MBytes/s over UDP/Gigabit 
Ethernet between 2 PCs. The NICs are from Intel and use the e1000 driver 
(MTU=1500). On the receive side, the computer has to process the data (real-time 
tasks doing signal processing work and using up 50% of the CPU time).

This app works OK with 2.6.7 and 2.6.8.1 : the app does not complain about lost 
messages.

But when I use the voluntary-preemt-2.6.8.1-P1 patch on the receiving PC, the 
app starts complaining about lost messages. And also, netstat -s -u shows that 
lots of UDP packets are lost (on the PC that receives the data).
[root@centaurus root]# netstat -u -s
Udp:
     8433 packets received
     0 packets to unknown port received.
     869 packet receive errors
     366 packets sent

I have already retried with the e1000 parameters RxIntDelay=0 and 
RxDescriptors=1024. This did not improve anything.

Note: I don't see any error message with dmesg nor in /var/log/messages.

I find the voluntary-preempt series very important and would really like it to 
make its way into the stock kernel. I would therefore gladly make additional 
tests to help you find the problem. Please give me directions.


	thanks for your help,

	P.O. Gaillard