Until now, we have been starting a large
number of VMs sequentially using a simple
"for i in vmcfg* ; do xm
create $i; done"
and this has the effect of starting
VMs sequentially but with some concurrency. The domain structure is created and
unpaused, and the "xm create completes". While the next iteration of the loop is
running "xm create" again, xen is busy scheduling and running any started
domains, which each boot their OS.
Since the total elapsed time to start a
large number of VMs in this way is significant, we looked for another way to
start them. If we change the script to:
"for i in vmcfg* ; do xm
create $i & done"
then many background tasks are spawned,
each running "xm create", and this has an interesting effect. When we monitor
with "xm top", we notice that all the domain structures are created and
completed first, then xen begins scheduling the domains and they boot. This works
well for 50 VMs.
However, when I try to start 100 VMs with
this script, all the domain structures get created, but then all of them are
dismantled and removed, and each one reports "Error: Device 0 (vif) could not be
connected. Hotplug scripts not working".
I've verified that, in fact, networking
is still working, because after all the VMs are destroyed, I can then start one or two without
error.
Any
idea what's breaking? Should I try changing the value of
DEVICE_CREATE_TIMEOUT in tools/python/xen/xend/server/DevController.py? If so,
what would I have to rebuild to use the changed file? Or is there some networking component that gets
overloaded? I have no problem starting the 100 VMs
sequentially.
brian carb
unisys corporation -
malvern, pa
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