Re: [PATCH v2 14/15] migration: Remove old preempt code around state maintainance

[Juan Quintela]

Peter Xu <peterx@redhat.com> wrote:
> With the new code to send pages in rp-return thread, there's little help to
> keep lots of the old code on maintaining the preempt state in migration
> thread, because the new way should always be faster..
>
> Then if we'll always send pages in the rp-return thread anyway, we don't
> need those logic to maintain preempt state anymore because now we serialize
> things using the mutex directly instead of using those fields.
>
> It's very unfortunate to have those code for a short period, but that's
> still one intermediate step that we noticed the next bottleneck on the
> migration thread.  Now what we can do best is to drop unnecessary code as
> long as the new code is stable to reduce the burden.  It's actually a good
> thing because the new "sending page in rp-return thread" model is (IMHO)
> even cleaner and with better performance.
>
> Remove the old code that was responsible for maintaining preempt states, at
> the meantime also remove x-postcopy-preempt-break-huge parameter because
> with concurrent sender threads we don't really need to break-huge anymore.
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>