A bug was reported about a very slow boot time and a 100% CPU usage of both Windows and Linux guests when running a VM with multiple virtio-serial devices (https://bugzilla.redhat.com/1528588).
For example, running a VM with 25 virtio-serial devices, each one with max_ports=511, could have a boot time of around 30 minutes. With this patch (and another patch to kvm) the boot time is reduced to approximately 3 minutes. The patch wraps all the changes made to the Memory Regions during the eventfd registrations in a memory regions transaction. I had to add a cleanup callback function to the EventNotifier struct, so it will be possible to use a transaction in the shutdown code path as well. Gal Hammer (3): qemu: add a cleanup callback function to EventNotifier virtio: postpone the execution of event_notifier_cleanup function virtio: improve virtio devices initialization time accel/kvm/kvm-all.c | 4 ++++ hw/virtio/virtio-bus.c | 19 +++++++++++-------- hw/virtio/virtio.c | 5 +++++ include/qemu/event_notifier.h | 1 + util/event_notifier-posix.c | 5 ++++- util/event_notifier-win32.c | 2 ++ 6 files changed, 27 insertions(+), 9 deletions(-) -- 2.7.5
