System load of 1 with CPU 100% idle

[Roger Pau Monné <roger.pau%entel.upc.edu@localhost>]

Hello,

I'm seeing some strange behaviour in a NetBSD installation with
RAIDframe, the load of the system goes to 1 with no reason, an then
goes to 0 again after a period of time (usually after some hours). The
output of the "top" command is the following:

load averages:  1.06,  1.02,  1.00;               up 2+04:59:19

                           18:19:14
28 processes: 1 runnable, 26 sleeping, 1 on CPU
CPU states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
Memory: 188M Act, 94M Inact, 112K Wired, 13M Exec, 257M File, 6020K Free
Swap: 5001M Total, 28M Used, 4973M Free

  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU COMMAND
  369 root      85    0   139M   36M RUN       14:03  0.00%  0.00% qemu-dm
    0 root     221    0     0K   43M raidiow   13:22  0.00%  0.00% [system]
  315 root      85    0   157M 8372K select     1:15  0.00%  0.00% python2.6
  637 root      85    0    53M 1804K select     0:12  0.00%  0.00% sshd
  184 root      85    0    21M 1604K kqueue     0:11  0.00%  0.00% syslogd
  291 root      85    0    15M 1260K select     0:02  0.00%  0.00% xenstored
19164 royger    43    0    15M 1616K CPU        0:00  0.00%  0.00% top
 6778 root      85    0    72M 4836K netio      0:00  0.00%  0.00% sshd
12123 royger    85    0    72M 3512K select     0:00  0.00%  0.00% sshd
14656 postfix   85    0    43M 3200K kqueue     0:00  0.00%  0.00% pickup
 1303 postfix   85    0    43M 2504K kqueue     0:00  0.00%  0.00% qmgr
  974 root      85    0    43M 2268K kqueue     0:00  0.00%  0.00% master
26858 nobody    85    0    44M 2240K select     0:00  0.00%  0.00% gmond
22081 royger    85    0    11M 1600K wait       0:00  0.00%  0.00% sh
24361 root      85    0    17M 1556K pipe_rd    0:00  0.00%  0.00% sshguard
  318 root      85    0   116M 1496K wait       0:00  0.00%  0.00% python2.6
  711 root      85    0    17M 1252K select     0:00  0.00%  0.00% screen-4.0.3
  862 root      85    0    11M 1244K ttyraw     0:00  0.00%  0.00% sh
  223 root      85    0    25M 1040K select     0:00  0.00%  0.00% xenconsoled
 1227 root      85    0  8728K 1016K nanoslp    0:00  0.00%  0.00% cron
    1 root      85    0    10M  988K wait       0:00  0.00%  0.00% init
  965 root      85    0    10M  960K ttyraw     0:00  0.00%  0.00% getty
  956 root      85    0    10M  960K ttyraw     0:00  0.00%  0.00% getty
  940 root      85    0    10M  960K ttyraw     0:00  0.00%  0.00% getty
  815 root      85    0    10M  960K ttyraw     0:00  0.00%  0.00% getty
  464 root      85    0    25M  944K nanoslp    0:00  0.00%  0.00% xenwatchdogd
  708 root      85    0    12M  812K kqueue     0:00  0.00%  0.00% inetd
  309 root      43    0    18M  852K parked     0:00  0.00%  0.00% xenbackendd

System is always in "raidiow" state, but at the same time CPU is
always 100% idle, so I don't know how I have an average load of 1 if
the CPU is not used. I have another system, with the same hardware and
configuration (except for the software disk RAID) that is reporting
load as expected, and is also running a Xen Dom0, so it makes me thing
it has something to do with the software RAID. Could someone provide
and explanation of what's happening?

Thanks and regards, Roger.