Re: + mm-introduce-reported-pages.patch added to -mm tree

[Mel Gorman <mgorman@techsingularity.net>]

On Fri, Nov 08, 2019 at 08:17:49AM -0800, Alexander Duyck wrote:
> > <SNIP>
> >
> > From your perspective, I see it's a bit annoying because in the final
> > result, the code should be identical. However, it'll be a lot clearer
> > during review what is required, what level of complexity optimisations
> > add and the performance of it. The changelog should include what metric
> > you are using to evaluate the performance, the test case and the delta. It
> > also will be easier from a debugging perspective as minimally a bisection
> > could identify if a bug was due to the core mechanism itself or one of
> > the optimisations.  Finally, it leaves open the possibility that someone
> > can evaluate a completely different set of optimisations. Whatever the
> > alternative approaches are, the actual interface to virtio ballon surely
> > is the same (I don't actually know, I just can't see why the virtio ABI
> > would be depend on how the pages are isolated, tracked and reported).
> 
> The virtio-balloon interface is the same at this point between my solution
> and Nitesh's. So the only real disagreement in terms of the two solutions
> is about keeping the bit in the page and the list manipulation versus the
> external bitmap and the hunt and peck approach.
> 

This is good news because it means that when/if Nitesh's approach is ready
that the optimisations can be reverted and the new approach applied and
give a like-like comparison if appropriate. The core feature and interface
to userspace would remain the same and stay available regardless of how
it's optimised. Maybe it's the weekend talking but I think structuring
the series like that will allow forward progress to be made.

-- 
Mel Gorman
SUSE Labs