Re: [libvirt] Save & Restore Synchronization
Erkan Unal wrote:
Hi,
I am using libvirt for qemu/kvm. I have following questions in terms of
save and restore (Version 0.6.2):
1) As I checked the libvirt code, restore command is asynchronous. There
is a macro called VIR_EXEC_NONBLOCK but there is no macro called
VIR_EXEC_BLOCK. Is it possible to execute the restore in blocking mode
so that I can measure the whole restore time?
Hm, the entire thing is *meant* to be synchronous. That being said, I'm not
exactly sure how we are achieving that (and maybe we aren't achieving it at
all). It used to be the case that the monitor wouldn't return until the
migration was finished, but that was changed long ago. I'd have to look into it
again; if it is indeed the case that it is not synchronous, then we'll probably
have to change it to loop on "info migrate" and wait for the migration to
complete in order to make it synchronous. That may also explain your errors below.
2) I tried to measure the time spent to save the VM. I am executing save
command and getting a timing. However when I execute the following
operations in order I got an error right after script issues the
restore operation (No delay between them):
"save->restore->save"
... the error is:
20:19:02.478: error : internal error Unable to open monitor path /dev/pts/3
libvir: QEMU error : internal error Unable to open monitor path /dev/pts/3
20:19:02.478: error : internal error unable to start guest: char device
redirected to /dev/pts/3
inet_listen: bind(ipv4,127.0.0.1,5912): Address already in use
inet_listen: FAILED
libvir: QEMU error : internal error unable to start guest: char device
redirected to /dev/pts/3
inet_listen: bind(ipv4,127.0.0.1,5912): Address already in use
inet_listen: FAILED
20:19:02.482: error : operation failed: failed to start VM
libvir: QEMU error : operation failed: failed to start VM
error: Failed to restore domain from /path/to/the/save/file
error: operation failed: failed to start VM
(You can find the detailed error report in the attachement when
LIBVIRT_DEBUG flag is 1)
I think that some of the cleanup is non-blocking which are cleanup of
pty device and vncserver. However, I am not sure if destroying the qemu
process is asynchronous??
Destroying the qemu process is definitely synchronous.
--
Chris Lalancette