Re: [LSF/MM/BPF TOPIC] Towards Unified and Extensible Memory Reclaim (reclaim_ext)

[Lorenzo Stoakes (Oracle)]

+cc Gregory

On Thu, Mar 26, 2026 at 08:06:13PM +0800, Kairui Song wrote:
> On Thu, Mar 26, 2026 at 10:05 AM Andrew Morton
> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, 25 Mar 2026 14:06:37 -0700 Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
> >
> > > We should unify both algorithms into a single code path.
> >
> > I'm here to ask the questions which others fear will sound dumb.
> >
> > Is it indeed the plan to maintain both implementations?  I thought the
> > long-term ambition was to knock MGLRU into shape and to drop the legacy LRU?
>
> I personally also agree on that, so far I'm not aware of any major
> issues with MGLRU except some corner cases that are not hard to fix.
> Once these are done, I don't see the need for more complexity.

Well... :)

What about the issues Gregory raised here?

https://lore.kernel.org/linux-mm/aaXM7xNSJaJBsety@gourry-fedora-PF4VCD3F/

>
>
> > And that Linus has expressed such a desire, but my googling fails me.

Yup I know, and it'd be ideal to have a single approach, but we definitely need
a little more assurance this time that it's the right choice :)

In any case I do agree with Shakeel that de-duplicating the code and 'stealing'
good ideas from it for both flavours of reclaim at least to start with is a good
way forwards.

Once we've done that, we can work towards eliminating the 'classic' reclaim if
the data supports it.

Thanks, Lorenzo