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

[Gregory Price <gourry@gourry.net>]

On Fri, Feb 27, 2026 at 09:55:52AM -0800, Shakeel Butt wrote:
> On Thu, Feb 26, 2026 at 03:54:22PM +0000, Matthew Wilcox 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 have very similar concerns. Though rather than ripping it out, I would like
> we put efforts in unifying the two reclaim mechanism (traditional & MGLRU) over
> improving MGLRU.
> 

I would agree.

If we could make the baseline MGLRU 2-generation and with behavioral
parity with the current LRU, then adding the additional generations
is just a mechanical change - and doesn't hurt anyone (default= 2 gen). 

But my understanding is MGLRU has behavior differences regarding its
preferences on how it ages anon vs file.

That mistake will cause significant pain in unifying them.

~Gregory