On Fri, Aug 12, 2022 at 03:34:53PM +0200, Claudio Imbrenda wrote: > This patch adds support for asynchronously tearing down a VM on Linux. > > When qemu terminates, either naturally or because of a fatal signal, > the VM is torn down. If the VM is huge, it can take a considerable > amount of time for it to be cleaned up. In case of a protected VM, it > might take even longer than a non-protected VM (this is the case on > s390x, for example). > > Some users might want to shut down a VM and restart it immediately, > without having to wait. This is especially true if management > infrastructure like libvirt is used. > > This patch implements a simple trick on Linux to allow qemu to return > immediately, with the teardown of the VM being performed > asynchronously. > > If the new commandline option -async-teardown is used, a new process is > spawned from qemu at startup, using the clone syscall, in such way that > it will share its address space with qemu.The new process will have the > name "cleanup/<QEMU_PID>". It will wait until qemu terminates > completely, and then it will exit itself. > > This allows qemu to terminate quickly, without having to wait for the > whole address space to be torn down. The cleanup process will exit > after qemu, so it will be the last user of the address space, and > therefore it will take care of the actual teardown. The cleanup > process will share the same cgroups as qemu, so both memory usage and > cpu time will be accounted properly. > > If possible, close_range will be used in the cleanup process to close > all open file descriptors. If it is not available or if it fails, /proc > will be used to determine which file descriptors to close. > > If the cleanup process is forcefully killed with SIGKILL before the > main qemu process has terminated completely, the mechanism is defeated > and the teardown will not be asynchronous. > > This feature can already be used with libvirt by adding the following > to the XML domain definition to pass the parameter to qemu directly: > > <commandline xmlns="http://libvirt.org/schemas/domain/qemu/1.0";> > <arg value='-async-teardown'/> > </commandline> > > Signed-off-by: Claudio Imbrenda <imbre...@linux.ibm.com> > Reviewed-by: Murilo Opsfelder Araujo <muri...@linux.ibm.com> > Tested-by: Murilo Opsfelder Araujo <muri...@linux.ibm.com> > --- > include/qemu/async-teardown.h | 22 +++++ > meson.build | 1 + > os-posix.c | 6 ++ > qemu-options.hx | 19 +++++ > util/async-teardown.c | 155 ++++++++++++++++++++++++++++++++++ > util/meson.build | 1 + > 6 files changed, 204 insertions(+) > create mode 100644 include/qemu/async-teardown.h > create mode 100644 util/async-teardown.c
Reviewed-by: Daniel P. Berrangé <berra...@redhat.com> With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
