Huge spikes in number of connections doing "PARSE"

hi,
i have a server with pg 8.3.11.

Every now and then, for no apparent reason (io normal, cpu usage normal,
web traffic normal) i see hundreds of connections in "PARSE" state.

to give some perspective - we're doing in the lowest traffic of the day
around 3000 transactions per second, with ~ 500-600 connections.

So. every now and then (couple of times per day at most). I see hundreds
(800-900) of connections in "PARSE" state.

I did notice one thing.

we do log output of ps axo user,pid,ppid,pgrp,%cpu,%mem,rss,lstart,nice,nlwp,sgi_p,cputime,tty,wchan:25,args
every 15 seconds or so.

And based on its output, I was able to get stats of "wchan" of all PARSE
pg processes when the problem was logged.
Results:

805 x semtimedop
10 x stext

Any ideas on what could be wrong? Machine was definitely not loaded most
of the times it happened.

The problem usually goes away in ~ 10-15 seconds.

Any hints? Suggestions?

Best regards,

depesz

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