How to diagnose a “context-switching ” storm problem ?

Hi，

My database server get sluggish suddenly ，I check the vmstat as below：

2010-04-07 04:03:15 procs memory swap io system cpu

2010-04-07 04:03:15 r b swpd free buff cache si so bi bo in cs us sy id wa

2010-04-07 14:04:27 3 0 0 2361272 272684 3096148 0 0 3 1445 973 14230 7 8 84 0

2010-04-07 14:05:27 2 0 0 2361092 272684 3096220 0 0 3 1804 1029 31852 8 10 81 1

2010-04-07 14:06:27 1 0 0 2362236 272684 3096564 0 0 3 1865 1135 19689 9 9 81 0

2010-04-07 14:07:27 1 0 0 2348400 272720 3101836 0 0 3 1582 1182 149461 15 17 67 0

2010-04-07 14:08:27 3 0 0 2392028 272840 3107600 0 0 3 3093 1275 203196 24 23 53 1

2010-04-07 14:09:27 3 1 0 2386224 272916 3107960 0 0 3 2486 1331 193299 26 22 52 0

2010-04-07 14:10:27 34 0 0 2332320 272980 3107944 0 0 3 1692 1082 214309 24 22 54 0

2010-04-07 14:11:27 1 0 0 2407432 273028 3108092 0 0 6 2770 1540 76643 29 13 57 1

2010-04-07 14:12:27 9 0 0 2358968 273104 3108388 0 0 7 2639 1466 10603 22 6 72 1

My postgres version: 8.1.3;

My OS version: Linux version 2.4.21-47.Elsmp((Red Hat Linux 3.2.3-54)

My CPU:

processor : 7

vendor_id : GenuineIntel

cpu family : 15

model : 6

model name : Intel(R) Xeon(TM) CPU 3.40GHz

stepping : 8

cpu MHz : 3400.262

cache size : 1024 KB

physical id : 1

I donnt know what make the “context-switching” storm ？

How should I investigate <javascript:;> the real reason ?

Could you please give me some advice ?

Best regards,

Ray Huang