Hi,

i have a SLES 10 SP4 guest running slowly in a SLES 11 SP4 host. The guest is running a small web application with a MySQL DB, an apache webserver and some perl scripts. The DB is not really busy, maybe some hundreds requests per day.
But the system performs slowly, especially on a console. Connecting with ssh, e.g. top need between 2 and 3 seconds to refresh its output. It's really not funny to work on the console.
The system has 4 virtual cpus and 8gb of ram. System was before a physical system which was migrated to a vm. The physical system just has 2 cpu's but is running fine. The host is very performanent, 8 cores and 96gb of ram. The host is running fine, no performance problem. And the guest is not a heavy load for it. It's KVM. Vmx flag is set on the host cores.
What i see is that the guest has constantly high si in top.

Here a typical example:

top - 14:12:31 up 38 min, 9 users, load average: 0.81, 0.69, 0.60
Tasks: 111 total, 2 running, 109 sleeping, 0 stopped, 0 zombie
Cpu0 : 0.0%us, 1.6%sy, 0.0%ni, 95.6%id, 0.0%wa, 0.0%hi, 2.8%si, 0.0%st
Cpu1 : 1.1%us, 1.1%sy, 0.0%ni, 86.8%id, 3.9%wa, 0.0%hi, 7.1%si, 0.0%st
Cpu2 : 0.6%us, 0.6%sy, 0.0%ni, 58.7%id, 0.0%wa, 5.2%hi, 34.8%si, 0.0%st
Cpu3 : 0.3%us, 0.3%sy, 0.0%ni, 85.8%id, 0.0%wa, 0.3%hi, 13.2%si, 0.0%st
Mem: 7995120k total, 1122420k used, 6872700k free, 75368k buffers
Swap: 2104472k total, 0k used, 2104472k free, 790208k cached

You see, the system isn't doing much. Very little IO, just a little bit load in user and system context, but much si.
How can i find out from where this si come from ? IIRC correctly, i had this problem already. I updated the system completely to SLES 11 SP4,
and the high si were history. But this was just for test, the system needs to be a SLES 10 SP4.
Maybe the kernel or some modules are the culprit ? I tried to update only the kernel, but it's not possible.
Tons of dependencies.

Thanks for any help.


Bernd