Re: [Qemu-devel] [PATCH v3 0/7] migration: pause-before-switchover

[Peter Xu <peterx@redhat.com>]

On Wed, Oct 18, 2017 at 06:40:06PM +0100, Dr. David Alan Gilbert (git) wrote:

[...]

> The precopy flow is:
> active->pre-switchover->device->completed
> 
> The postcopy flow is:
> active->pre-switchover->postcopy-active->completed

The naming is still slightly confusing to me:

(1) we have a capability called "pause-before-switchover", so it feels
    like there is something called "switchover" and if we enable this
    we'll pause before that point;

(2) we have a new status "pre-switchover", it feels like that's the
    point before we are in "switchover" state;

(3) we don't really have a "switchover" state, but instead it's called
    "device" which is exactly the "switchover" action.

Considering (1) and (2), I would prefer "device" state to be just
"switchover"...

Further, not sure we can unify the state transition as well (say, we
add this switchover state even without cap "pause-before-switchover"
set, although it does not make much sense itself). Then, we can also
unify the precopy/postcopy state machine into one:

active->
  [pre-switchover->]      (optional, decided by "pause-before-switchover")
    switchover->
      [postcopy-active->] (optional, decided by "postcopy-arm")
        completed

(Sorry I am discussing the naming again instead of reviewing real
 stuff!)

-- 
Peter Xu