2.6.17.7 leading to doubling system CPU usage?

[Robin H. Johnson]

(Please CC on responses, I'm not subscribed to LKML).

Short problem summary: 
Between 2.6.17.4 and 2.6.17.7, SYS cpu usage doubled.

In short, before the upgrade, our DB cpu usage breakdown was:
		SYS	USER NICE IDLE IOWAIT IRQ SOFTIRQ
BEFORE  28% 71%  0%   80%  15%    1%  5% 
AFTER   57% 93%  0%   41%  0%     1%  7%
(See the graphs for more detail.  http://isohunt.com/img/stuff/munin-capture/db.isohunt.com-cpu.html)

Notice the big jump in SYS. USER is up a little as well.

IOWAIT should be ignored as we did a RAM upgrade to try and alleviate
some of the work on this box.

The userspace load on this box doesn't vary by more than 10% when
examined at the same time each day.

Here is a complete snapshot set of graphs for the machine in question:
http://isohunt.com/img/stuff/munin-capture/db.isohunt.com.html

Other misc answers before they get asked of me:
- The motherboard used is the Tyan S2881.
- There are two reboots in the graph timeline. The first on 29th was for
  the upgrade to 2.6.17.7. The second reboot was on the 31st, was the
  RAM being doubled.

Kernel config:
http://isohunt.com/img/stuff/munin-capture/kernel-config-2.6.17.7
http://isohunt.com/img/stuff/munin-capture/kernel-config-2.6.17.4
(oldconfig on .7 added CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y).

-- 
Robin Hugh Johnson
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