[PATCH v10 12/14] mm: multi-gen LRU: debugfs interface

[Andrew Morton]

On Fri, 15 Apr 2022 18:03:16 -0600 Yu Zhao <yuzhao at google.com> wrote:

> > Presumably sysfs is the place.  Fully documented and with usage
> > examples in the changelog so we can carefully review the proposed
> > extensions to Linux's ABI.  Extensions which must be maintained
> > unchanged for all time.
> 
> Eventually, yes. There still is a long way to go. Rest assured, this
> is something Google will keep investing resources on.

So.  The plan is to put these interfaces in debugfs for now, with a
view to migrating stabilized interfaces into sysfs (or procfs or
whatever) once end-user requirements and use cases are better
understood?

If so, that sounds totally great to me.  But it should have been in
the darn changelog!  This is the sort of thing which we care about most
keenly.

It would be helpful for reviewers to understand the proposed timeline
for this process, because the entire feature isn't really real until
this is completed, is it?  I do think we should get this nailed down
relatively rapidly, otherwise people will be reluctant to invest much
into a moving target.

And I must say, I see dissonance between the overall maturity of the
feature as described in these emails versus the immaturity of these
userspace control interfaces.  What's happening there?