Re: [PATCH v14 3/6] mm: Introduce Reported pages

[Alexander Duyck]

On Thu, Nov 28, 2019 at 1:22 AM Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Nov 27, 2019 at 01:55:02PM -0800, Alexander Duyck wrote:

< snip >

> > >
> > > Which in itself could be an optimisation patch. Maybe it'll be enough that
> > > keeping track of the count is not worthwhile. Either way, the separate
> > > patch could have supporting data on how much it improves the speed of
> > > reporting pages so it can be compared to any other optimisation that
> > > may be proposed. Supporting data would also help make the case that any
> > > complexity introduced by the optimisation is worthwhile.
> >
> > I'll see what I can do to break this apart. I'm just not a fan of redoing
> > the work multiple times so that I can have a non-optimized version versus
> > an optimized one.
> >
>
> While I understand that, right now the optimisations are blocking the
> feature itself which is also not a situation you want to be in.

I'll see what I can do. I can probably replace the reference count and
zone flags with an atomic state in the prdev that cycles between
inactive, requested, and active. With that I can at least guarantee
that we shouldn't have any races that result in us missing freed
pages. The only downside is that I have to keep a boolean in the
__free_one_page call so that when we free back the reported pages we
don't retrigger the reporting and cause an infinite loop.