Re: [PATCH 18/20] migration: Postcopy preemption enablement

[Peter Xu]

On Tue, Feb 22, 2022 at 10:52:23AM +0000, Dr. David Alan Gilbert wrote:
> This does get a bit complicated, which worries me a bit; the code here
> is already quite complicated.

Right, it's the way I chose in this patchset on solving this problem.  Not
sure whether there's any better and easier way.

For example, we could have used a new thread to send requested pages, and
synchronize it with the main thread.  But that'll need other kind of
complexity, and I can't quickly tell whether that'll be better.

For this single patch, more than half of the complexity comes from the
ability to interrupt sending one huge page half-way.  It's a bit of a pity
that, that part will be noop ultimately when with doublemap.

However I kept those only because we don't know when doublemap will be
ready, not to say, landing.  Meanwhile we can't assume all kernels will
have doublemap even in the future.

> (If you repost, there are a few 'channel' variables that could probably
> be 'unsigned' rather than int)

That I can do for sure.

> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Thanks,

-- 
Peter Xu