2.6.10: kswapd spins like crazy

["Terje Fåberg" <terje_fb@yahoo.no>]

I recently upgraded my desktop from 2.4.28 to
2.6.10. Even under moderate memory pressure kswapd
regularly eats almost all available cpu time 
whenever there is a little more IO throughput,
like copying large files. The system is extremely
sluggish during this. The system load goes up to 
7.5 or more.
 
This is a Pentium3-866 with 768MB RAM, 2x1GB 
swap partitions, vanilla 2.6.10. The strange 
behaviour starts at about 200 MB of swap in use.
2.4.28 masters the same workload without any
problems.

vmstat:
procs -----------memory---------- 
 r  b   swpd   free   buff  cache
 6  1 428012   4868  33236 347184
---swap-- -----io---- --system-- ----cpu----
 si   so    bi    bo   in    cs us sy id wa
 10    7   147   120  108   111 19 10 68  3

Is there anything I can do to track this down?

Regards, 
Terje