[Spread-users] Tuning Windows XP for Spread

Doug Palmer Doug.Palmer at csiro.au
Tue Jul 10 21:01:35 EDT 2007

I think I've traced the behaviour that I've seen to problems with
Windows XP UDP performance.

We've been running 4-5 spread daemons at High priority. However, we keep
on seeing the tok_hurry count go up and cases where one spread daemon
(apparently because it's the segment leader) suddenly develop a huge
number of s_retrans counts, which just keeps on going up. At the same
time, the spread deamons start growing in memory size and eventually
lock up.

When I run spsend and sprecv, using a broadcast address, no packets are
lost. When I have another process running that uses CPU, the packet loss
is of the order of 1% packet loss for every 10% of CPU. 

This is across a local network where both machines are plugged into the
same switch. Making sprecv High priority improves things somewhat, but
there is still significant packet loss.

This seems to be an OS problem rather than a network problem, since
other sprecv instances simultaneously running on unloaded machines lose
no packets.

First-off, this looks to be a problem with Windows XP; losing packets at
20% CPU is pretty pathetic. I'm unwilling to shift the process to
Real-time priority, thanks to the lock-up problem. However, can anybody
suggest any tuning that I can do to Windows XP to make it more

However, I suspect that the poor behaviour of XP is exposing a problem
with spread where recovery attempts are causing thrashing and eventual

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