problems running many guests

[Karl Rister <kmr@us.ibm.com>]

Hi

I have been trying to do some testing of a large number of guests (72) on a 
big multi-node IBM box (8 sockets, 32 cores, 128GB) and I am having various 
issues with the guests.  I can get the guests to boot, but then I start to 
have problems.  Some guests appear to stall doing I/O and some become 
unresponsive and spin their single vcpu at 100%.

Each guest is configured with 1 vcpu and 1000MB of memory.  The single virtual 
disk is backed by a LVM volume.  Both the guest and host are running custom 
kernels.

I have tried kvm-67, kvm-64, and kvm-62 (not functional at all).  I have 
cloned both the kvm and kvm-userspace repositories and am building the tagged 
changesets from each.

Here are a few of the various things I have tried: virtio and emulated devices 
for the nic and disk; mixed virtio and emulated devices; kvm-clock and 
clock=jiffies.

Any help in pinpointing the problem would be appreciated.

Thanks.

-- 
Karl Rister
IBM Linux Performance Team
kmr@us.ibm.com
(512) 838-1553 (t/l 678)

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