Re: [Qemu-devel] [PATCH 6/8] migration: implementation of hook_ram_sync

[Denis V. Lunev]

On 10/07/2015 12:44 PM, Paolo Bonzini wrote:
> On 07/10/2015 08:20, Denis V. Lunev wrote:
> > +        if (migrate_is_test()) {
> > +            /* since no data is transfered during estimation all
> > +               all measurements below will be incorrect.
> > +               as well no need for delays. */
> > +            continue;
> > +        }
> By applying delays, you can also test migration using bandwidth
> limitations and try to estimate whether it will converge or not.
> Perhaps if you use writev_buffer to implement the test QEMUFile you do
> not need this anymore.
>
> Paolo
you see, your proposal would be better for emulation approach.
In this case the 'test' will take much more time and may be
it will be better for testing purpose.

Here we are solving a bit different problem. We are trying to
collect reasonable data to make a prediction for migration
time and downtime for cluster or cloud management where
VMs are hosted on different physical hosts and are migrated
from one host to another using different policies.

In this case we need to make an estimate to check migration
feasibility and it would be nice if we will be able to achieve
this goal in the minimal period of time with a minimal overhead :)))
OK, this sounds a bit trivial :)

On the other hand this code could be used for testing that is
why I have spoken about this set.

Den