MGLRU Merged For Linux 6.1

[kylew77]

It's not "thousands". It's not even *"dozens"*, and that's on a 4GB machine. You massively underestimate the bloat of the modern web.

The fact that midrange Chromebooks can ship with 4GB of RAM and you have to search pretty high up the market for an 8GB or 16GB model and that they run well is a testament to MGLRU. I had a 4GB Chromebook and used it from 2016 to 2021 and only had one hard power off because I ran out of memory and I abused the heck out of that 4GB of RAM asking it to open a couple dozen Chrome tabs!

[arQon]

At least some of the members of this forum complain about abysmal performance (due to memory pressure) when they open thousands of windows/tabs on their desktop, and this may help them (at least some of the time).

It's not "thousands". It's not even *"dozens"*, and that's on a 4GB machine. You massively underestimate the bloat of the modern web.

Even without that, it's trivial to fill memory. VMs, containers, and so on have made it so that even 16GB means a machine is under-provisioned even *without* a hundred tabs of garbage in a browser, and Linux's inability to cope with that in anything resembling a sane way is one of the most significant problems the entire ecosystem currently has. When trying to start even a trivial program locks a machine solid for minutes even with swap on an SSD - or, worse, sets off a garbage oomd that wipes out hours of work - something is flat-out *broken*.

I'm not one of the people with weak machines, but blaming them for the OS's failures is both dishonest and a big part of why this has taken *decades* to actually get (mostly) fixed.

[fitzie]

maple tree is another datastructure contribution by matthew wilcox to provide a tree datastructure that supports ranges and provides rcu capabilities. his previous work was improving the radix tree api (which he called xarray). he gives great talks and it seems he really focuses on making the apis easy to use for developers.

It seems the RCU capabilities of the Maple Tree is not implemented yet. more detail in this lfsmm submit discussion: https://www.youtube.com/watch?v=12GNb53g3ZA

[fitzie]

Since it's mostly for memory-constrained systems, it's not something that needs to be enabled by default. On the other hand, once it's proven to not degrade anything, why not?

Afaik, Arch just uses upstream configs so it probably won't enable it.

That said, anyone knows anything about this Maple Tree structure?

maple tree is another datastructure contribution by matthew wilcox to provide a tree datastructure that supports ranges and provides rcu capabilities. his previous work was improving the radix tree api (which he called xarray). he gives great talks and it seems he really focuses on making the apis easy to use for developers.

[CommunityMember]

Since it's mostly for memory-constrained systems, it's not something that needs to be enabled by default.

At least some of the members of this forum complain about abysmal performance (due to memory pressure) when they open thousands of windows/tabs on their desktop, and this may help them (at least some of the time).

On the other hand, once it's proven to not degrade anything, why not?

As with any change, there are almost certainly edge cases or synthetics that can show degradation. The question is whether those cases can be addressed, or are sufficiently rare to not be a strong consideration in any decision. It should be noted that millions of real world devices are already using MGLRU with good results being reported.

[murlakatamenka]

Arch and others will definitely enable it. Maybe I will even consider stop building my own kernel...

xanmod has other useful patches, I'll still keep using it

[ihatemichael]

How does one enables this? Is there a boot parameter or something like that?

[bug77]

Finally, wonderful!
But too bad it's not enabled by default.
Considering that this will probably be the next LTS and next Debian release using it by default, I'm not sure they will enable it before building it.

Since it's mostly for memory-constrained systems, it's not something that needs to be enabled by default. On the other hand, once it's proven to not degrade anything, why not?

Arch and others will definitely enable it. Maybe I will even consider stop building my own kernel...

Afaik, Arch just uses upstream configs so it probably won't enable it.

That said, anyone knows anything about this Maple Tree structure?

[CommunityMember]

But too bad it's not enabled by default.

Not enabled by default is the standard approach for significant replacement functionality (with the notable exception of security updates).

Considering that this will probably be the next LTS and next Debian release using it by default, I'm not sure they will enable it before building it.

You and others who want MGLRU to be enabled will need to start asking the debian kernel team to add it to their configs (and what they need to be convinced to do so).

[MadCatX]

Excellent! I'm really looking forward to see how much of a difference I'll notice in practice.