High load on Xen guests

Question

We're facing a weird issue with a freshly installed Xen (4.2) system.

The server is an Intel SR1690WB equipped with 4x1Tb HDD and with a RS2BL040 RAID card which configured to use RAID10.

The problem is that any newly spawned paravirtualized guest OS (Debian Squeeze) is working with very high load (70-80% use of CPU, mostly caused by events/0 or events/1) no matter what they're doing (serving a dynamic page, or just simply downloading an iso file).

Each guest configured to use 2 CPU cores and 4gb RAM.

Just hoping there's some misconfiguration on the Dom0, but what can cause these terrible loads?

Please let me know if i can clarify my question.

How much of that "CPU load" is actually iowait? – EEAA Feb 14 '12 at 13:32 — EEAA, Feb 14 '12 at 13:32
@ErikA iostat gives me 0.09 %iowait. – fabrik Feb 14 '12 at 13:38 — fabrik, Feb 14 '12 at 13:38

score 1 · Accepted Answer · answered Feb 14 '12 at 14:30

Fortunately the problem was found in our configuration.

After pinning a CPU core to Dom0 (instead of starting with the nosmp parameter) in grub options with

GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=1024M dom0_max_vcpus=1 dom0_vcpus_pin"

All of the guest OS's are running healthy and fast. :)

High load on Xen guests

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