Odd news transit performance problem

[Dave Williams]

Folks,

 we're seeing a somewhat puzzling scenario with a FreeBSD 4.9RC
box of an October '03 vintage kernel. The box is currently running
innd for news transit, and in circumstances of heavy traffic load
performance on the machine drops through the floor. 

Various reporting tools (systat, vmstat, top, etc) report that the
box is idle - there's no significant contention for memory, disk,
network, etc. that we can see and actually bouncing the box seems
to bring performance back up to speed again for a period - restarting
innd doesn't have the same effect.

The machine is a 2.8GHz Xeon, Intel  10/100 and 1000 NICs, 
is running with two onboard LSI 53C{mumble} scsi controllers,
device polling enabled, HZ=1000, and MAXDSIZ set to 1GB
and MAXSSIZ/DFLDSIZ. We're a bit stumped as to where to look
at the moment. :(

Thanks
Dave
-- 
Dave Williams
dave at uk.clara.net