Re: [LSF/MM/BPF TOPIC] Improving MGLRU

[Axel Rasmussen <axelrasmussen@google.com>]

On Thu, Feb 26, 2026 at 7:54 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Fri, Feb 20, 2026 at 01:25:33AM +0800, Kairui Song wrote:
> > MGLRU has been introduced in the mainline for years, but we still have two LRUs
> > today. There are many reasons MGLRU is still not the only LRU implementation in
> > the kernel.
>
> To my mind, the biggest problem with MGLRU is that Google dumped it on us
> and ran away.  Commit 44958000bada claimed that it was now maintained and
> added three people as maintainers.  In the six months since that commit,
> none of those three people have any commits in mm/!  This is a shameful
> state of affairs.
>
> I say rip it out.

I acknowledge this is a big problem. We have let the community down
here, and we plan to correct this starting in April, e.g. by working
together with Kairui and others to address outstanding issues.

As part of qualifying MGLRU in our own production environment we've
been debugging and developing expertise on a variety of kernel
versions up to 6.18. Priority has been given to this qualification,
and did not offer enough attention to upstream engagement. We plan to
post any fixes / improvements discovered during this process to the
mailing list.