Stats collector eats my CPU

This is top of my 'top':

15483 postgres 15 0 147m 31m 284 R 17 0.8 29033:23 postgres
24599 postgres 15 0 1293m 274m 231m S 2 6.9 0:02.05 postgres
24598 postgres 15 0 1258m 99m 88m S 1 2.5 0:00.62 postgres

the 15483 process is stats collector. At the moment server is almost
idle but the stats collector is constantly taking 15-17% of CPU.

My statistics related settings looks like this:

track_activities on
track_counts on
default_statistics_target 100

I don't know if it matters at all, but maybe the reason is that the
cluster is very large in the term of relation number (many schemes
with identical table set).

------------------------------------------------------------------------------------
select count(*) from pg_class;
count
--------
257477
------------------------------------------------------------------------------------

I'm using PostgreSQL 8.3.1 on x86_64-redhat-linux-gnu, compiled by GCC
gcc (GCC) 4.1.2 20070626 (Red Hat 4.1.2-14)

The 15% isn't much and I can afford it but what's strange there is
really small trafic at the moment (in average about 5%), and the DML's
are about 5% of it. So what is the stat collector doing? I'm affraid
what will happend if the real query traffic will increase.

Maybe the PGSTAT_STAT_INTERVAL is the issue in my case (vary large
schema)? The PG is from yum.

Any suggestions? Should I worry? Can I do anything about it?
(adjusting schema will not be easy :D )

Wojtek Strzalka