[Qemu-devel] [PATCH 0/3 v2] virtio: improve virtio devices initialization time

[Gal Hammer <ghammer@redhat.com>]

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