[CentOS-virt] steadily increasing/high loadavg without i/o wait or cpu utilization

Fri Nov 20 08:13:18 UTC 2009
Günter Zimmermann <guenter.zimmermann at gmx.at>

Hi all,

I just installed centos 5.4 xen-kernel on intel core i5 machine as dom0.
After some hours of syncing a raid10 array (8 sata disk) I noticed a
steadily increasing loadavg. I think without reasonable i/o wait or cpu
utilization the loadavg on this system should be very lower. If this
loadavg is normal I would be greatful if somone could explain why. The
screenshots below show that there is neither much i/o wait nor much cpu
utilization.

top - 09:10:25 up  9:26,  1 user,  load average: 7.24, 7.63, 7.72
Tasks: 116 total,   4 running, 112 sleeping,   0 stopped,   0 zombie
Cpu0  :  0.0%us, 42.5%sy,  0.0%ni, 57.5%id,  0.0%wa,  0.0%hi,  0.0%si, 
0.0%st
Cpu1  :  0.0%us,  1.3%sy,  0.0%ni, 97.7%id,  0.0%wa,  0.0%hi,  0.0%si, 
1.0%st
Cpu2  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si, 
0.0%st
Cpu3  :  0.0%us, 10.0%sy,  0.0%ni, 89.0%id,  0.0%wa,  0.0%hi,  0.0%si, 
1.0%st
Mem:   7805952k total,   809612k used,  6996340k free,   112092k buffers
Swap:        0k total,        0k used,        0k free,   341304k cached

[root at vserver ~]# iostat -d -x  sda sdb sdc sdd sde sdf sg sdh
Linux 2.6.18-164.6.1.el5xen (vserver.zimmermann.com)     20.11.2009

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
avgqu-sz   await  svctm  %util
sda            1364,57     0,66 1820,12  0,89 25477,44    12,37   
14,00     1,11    0,61   0,41  75,10
sdb            1167,12     0,68 2017,45  0,89 25476,53    12,47   
12,63     1,16    0,57   0,39  79,49
sdc            1308,06     0,66 1876,65  0,91 25477,64    12,50   
13,58     1,14    0,61   0,42  78,73
sdd            1267,27     0,66 1917,28  0,92 25476,32    12,57   
13,29     1,09    0,57   0,42  80,16
sde            1146,76     0,63 2037,99  0,87 25477,94    11,96   
12,50     0,98    0,48   0,31  63,80
sdf            1126,88     0,64 2057,62  0,87 25475,99    12,02   
12,38     1,08    0,52   0,34  69,89
sdh             472,21     0,66 2712,31  0,92 25476,13    12,43    
9,39     0,66    0,24   0,15  41,03

[root at vserver ~]# cat /proc/loadavg
7.22 7.58 7.69 8/129 23348

Best regards,
Günter Zimmermann