libvirt users - Mar 2014 - Live migration process in src/qemu_driver.ca

​Hello,

I have been trying to track different phases of a live migration process. I
am using libvirt ​with qemu-kvm. I am issuing migration commands using
virsh.

Now, I want to measure the time spent in each phase of live migration,
e.g., pre-copy and stop-copy. I stumbled upon the file qemu_driver.c. It
has functions like

qemudDomainMigratePrepare2
qemudDomainMigratePerform
qemudDomainMigrateFinish2

I want to know whether qemudDomainMigratePerform and
qemudDomainMigrateFinish2 directly map to the pre-copy and stop-copy phase?
or the qemudDomainMigratePerform function performs both of them?

Any pointers or suggestions will be greatly appreciated.

Regards
----------------------
Md. Faizul Bari

PhD Student
David R. Cheriton School of Computer Science
University of Waterloo
{http://www.cs.uwaterloo.ca/~mfbari}
[My mind rebels at stagnation! Give me problems! Give me work!]

On 03/20/2014 10:05 AM, Faizul Bari wrote:
> ​Hello,
> 
> I have been trying to track different phases of a live migration process. I
> am using libvirt ​with qemu-kvm. I am issuing migration commands using
> virsh.
> 
> Now, I want to measure the time spent in each phase of live migration,
> e.g., pre-copy and stop-copy. I stumbled upon the file qemu_driver.c. It
> has functions like
> 
> qemudDomainMigratePrepare2
> qemudDomainMigratePerform
> qemudDomainMigrateFinish2
These functions perform different handshakes between the two libvirt
ends of the migration.  However, the entire migration is done by a
single qemu monitor command, and it is that monitor command that further
divides the work into phases such as pre-copy and stop-copy.
> 
> I want to know whether qemudDomainMigratePerform and
> qemudDomainMigrateFinish2 directly map to the pre-copy and stop-copy phase?
> or the qemudDomainMigratePerform function performs both of them?
The MigratePerform function is the one place that calls the qemu monitor
command.  I know there have been proposals upstream in qemu to add
additional statistics in 'query-migrate' monitor command; perhaps there
is still more work needed in libvirt to grab those additional statistics
in a manner that can be exposed to the user.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

Thanks Eric.

So, I need to look at QEMU. Do you know which files/functions should I look
at?

​--
Faiz​


On Thu, Mar 20, 2014 at 12:41 PM, Eric Blake <eblake@redhat.com> wrote:
> On 03/20/2014 10:05 AM, Faizul Bari wrote:
> > ​Hello,
> >
> > I have been trying to track different phases of a live migration
> process. I
> > am using libvirt ​with qemu-kvm. I am issuing migration commands using
> > virsh.
> >
> > Now, I want to measure the time spent in each phase of live migration,
> > e.g., pre-copy and stop-copy. I stumbled upon the file qemu_driver.c.
It
> > has functions like
> >
> > qemudDomainMigratePrepare2
> > qemudDomainMigratePerform
> > qemudDomainMigrateFinish2
>
> These functions perform different handshakes between the two libvirt
> ends of the migration.  However, the entire migration is done by a
> single qemu monitor command, and it is that monitor command that further
> divides the work into phases such as pre-copy and stop-copy.
>
> >
> > I want to know whether qemudDomainMigratePerform and
> > qemudDomainMigrateFinish2 directly map to the pre-copy and stop-copy
> phase?
> > or the qemudDomainMigratePerform function performs both of them?
>
> The MigratePerform function is the one place that calls the qemu monitor
> command.  I know there have been proposals upstream in qemu to add
> additional statistics in 'query-migrate' monitor command; perhaps
there
> is still more work needed in libvirt to grab those additional statistics
> in a manner that can be exposed to the user.
>
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>