Hi!
Occasionally of late, I've seen a few cases where libvirtd cpu usage
shoots up to 100% and stays there indefinitely. This seems to happen
when a QEMU VM is starting up, although on one occasion I *think* I
saw it happen after a QEMU VM was p2p-migrated.
Doing strace -f -p <libvirtd pid> reveals a flood of poll() functions calls
like these:
[pid 1690] poll([{fd=3, events=POLLIN}, {fd=6, events=POLLIN}, {fd=12, events=POLLIN|POLLERR|POLLHUP}, {fd=11, events=POLLIN|POLLERR|POLLHUP}, {fd=10, events=POLLIN|POLLERR|POLLHUP}, {fd=9, events=POLLIN|POLLERR|POLLHUP}, {fd=24, events=POLLIN|POLLERR|POLLHUP}, {fd=21, events=POLLOUT}, {fd=14, events=POLLIN}, {fd=15, events=POLLIN}, {fd=16, events=POLLIN}, {fd=17, events=POLLIN}, {fd=21, events=POLLIN|POLLERR|POLLHUP}, {fd=20, events=POLLIN|POLLERR|POLLHUP}], 14, -1) = 1 ([{fd=21, revents=POLLOUT}])
It seems that because 1 is returned each time, libvirtd just goes
crazy dealing with fd-3, but I have no idea what fd-3 is.
Restarting libvirtd fixes the high load, and then everything just
goes back to chugging along as usual.
This is on libvirt 0.8.5 with qemu 0.12.5 on a debian Squeeze system
(the libvirt is compiled by hand).
I'm not sure what's causing it, whether it's a bug in my own code
somehow or inside libvirtd. I'd appreciate some help on how to debug
this problem further -- restarting libvirtd is kind of a pain for
me, because my application, which monitors the health on the node,
maintains open connections to 'qemu:///system' and would thus have
to restart itself as well...
--Igor
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