Re: [PATCH v2 2/6] tests/qtests: remove migration test iterations config

[Juan Quintela]

Daniel P. Berrangé <berrange@redhat.com> wrote:
> The 'unsigned int interations' config for migration is somewhat
> overkill. Most tests don't set it, and a value of '0' is treated
> as equivalent to '1'. The only test that does set it, xbzrle,
> used a value of '2'.
>
> This setting, however, only relates to the migration iterations
> that take place prior to allowing convergence. IOW, on top of
> this iteration count, there is always at least 1 further migration
> iteration done to deal with pages that are dirtied during the
> previous iteration(s).
>
> IOW, even with iterations==1, the xbzrle test will be running for
> a minimum of 2 iterations. With this in mind we can simplify the
> code and just get rid of the special case.

Perhaps the old code was already wrong, but we need at least three
iterations for the xbzrle test:
- 1st iteration: xbzrle is not used, nothing is on cache.
- 2nd iteration: pages are put into cache, no xbzrle is used because
  there is no previous page.
- 3rd iteration: We really use xbzrle now against the copy of the
  previous iterations.

And yes, this should be commented somewhere.

Later, Juan.