Re: [PATCH 0/1] Add swappiness argument to memory.reclaim

[Dan Schatzberg <schatzberg.dan@gmail.com>]

On Thu, Nov 30, 2023 at 12:30:27PM -0800, Shakeel Butt wrote:
> On Thu, Nov 30, 2023 at 11:47 AM Dan Schatzberg
> <schatzberg.dan@gmail.com> wrote:
> >
> > On Thu, Nov 30, 2023 at 11:56:42AM -0500, Johannes Weiner wrote:
> > > [...]
> > > So I wouldn't say it's merely a reclaim hint. It controls a very
> > > concrete and influential factor in VM decision making. And since the
> > > global swappiness is long-established ABI, I don't expect its meaning
> > > to change significantly any time soon.
> >
> > I want to add to this last point. While swappiness does not have
> > terribly well-defined semantics - it is the (only?) existing mechanism
> > to control balance between anon and file reclaim. I'm merely
> > advocating for the ability to adjust swappiness during proactive
> > reclaim separately from reactive reclaim. To what degree the behavior
> > and semantics of swappiness change is a bit orthogonal here.
> 
> Let me ask my question in this chain as it might have been missed:
> 
> Whatever the semantics of swappiness are (including the edge cases
> like no swap, file_is_tiny, trim cache), should the reclaim code treat
> the global swappiness and user-provided swappiness differently?

I can't think of any reason why we would want swappiness interpreted
differently if it's provided at proactive reclaim time vs
globally. Did you have something in mind here?