libvirt 1.3.3 seems to have introduced some kind of issue on CentOS 6 (no systemd). After upgrading, libvirt would take an incredibly long time to get to a state where it would actually respond to a simple 'virsh list' command. Looking at verbose output showed this repeating at exactly 30s intervals 2016-04-12 19:40:57.142+0000: 14929: info : virEventPollDispatchHandles:507 : EVENT_POLL_DISPATCH_HANDLE: watch=1 events=1 2016-04-12 19:40:57.142+0000: 14929: info : virEventPollRunOnce:641 : EVENT_POLL_RUN: nhandles=116 timeout=-1 2016-04-12 19:40:57.143+0000: 15223: info : virObjectRef:296 : OBJECT_REF: obj=0x7fb944181bc0 2016-04-12 19:40:57.144+0000: 15223: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb944181bc0 2016-04-12 19:40:57.157+0000: 15223: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb944253020 2016-04-12 19:40:57.157+0000: 15223: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb944309450 2016-04-12 19:40:57.157+0000: 15223: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb94400ca90 2016-04-12 19:41:27.147+0000: 15224: info : virDBusCall:1577 : DBUS_METHOD_REPLY: 'org.freedesktop.DBus.ListActivatableNames' on '/org/freedesktop/DBus' at 'org.freedesktop.DBus' 2016-04-12 19:41:27.148+0000: 15224: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb94400ca90 2016-04-12 19:41:27.148+0000: 15224: info : virObjectRef:296 : OBJECT_REF: obj=0x7fb94400ca90 2016-04-12 19:41:27.148+0000: 15224: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb94400ca90 2016-04-12 19:41:27.148+0000: 15224: info : virObjectRef:296 : OBJECT_REF: obj=0x7fb94400ca90 2016-04-12 19:41:27.151+0000: 15224: info : virObjectUnref:259 : OBJECT_UNREF: obj=0x7fb94400ca90 2016-04-12 19:41:27.151+0000: 15224: info : virObjectRef:296 : OBJECT_REF: obj=0x7fb860000e30 2016-04-12 19:41:27.151+0000: 15224: info : virEventPollUpdateHandle:152 : EVENT_POLL_UPDATE_HANDLE: watch=58 events=15 2016-04-12 19:41:27.151+0000: 15224: info : qemuMonitorSend:1005 : QEMU_MONITOR_SEND_MSG: mon=0x7fb860000e30 msg={"execute":"query-status","id":"libvirt-7"} fd=-1 Looking at the dbus src, there's a 30s timeout defined here: src/util/virdbus.c:# define VIR_DBUS_METHOD_CALL_TIMEOUT_MILLIS 30 * 1000 So, for some reason libvirt is trying to call a dbus method before every KVM instance start. This leads to absurdly long startup times. This behavior was not present in 1.3.1. My workaround was to just recompile with '--with-firewalld=no --with-dbus=no', which seems to have worked. There's not really anything useful for libvirt to be talking to via dbus (in our environment), so no big loss there.