MGLRU Looks Like One Of The Best Linux Kernel Innovations Of The Year

Hopefully being mainlined next cycle with Linux 6.1 is the Multi-Gen LRU, or better known as MGLRU, as a superior alternative to the kernel's existing page reclamation code. Assuming it lands for Linux 6.1 as the last complete kernel cycle of 2022, this would make it one of the most exciting innovations to make it into the kernel this year.

MGLRU benchmarks continue to look very promising across a wide variety of workloads and a diverse spectrum of hardware. From Chrome OS and Android up through desktops/workstations and even servers, MGLRU is able to often deliver better performance due to being less taxing than the existing page reclamation code that has also been acknowledged as often making poor eviction choices.

Jesse Barnes‎ and Rom Lemarchand, both of Google, presented yesterday at Linux Plumbers Conference 2022 (LPC2022) on the latest MGLRU happenings. They reiterated the expectation that MGLRU should make it to mainline with Linux 6.1, there are numerous kernel downstreams and backports already using the code in production, and benchmarks continue to look promising.

Once mainlined, the next obstacle for the involved Google engineers is to get MGLRU to the point that it could be safely enabled by default. Before considering it by default, they need much more performance testing and benchmarking to ensure MGLRU is in good shape and won't regress existing workloads. They also hope to integrate MGLRU with eBPF to open up even more possibilities.

Those wishing to learn more can see the presentation slide deck or the video embedded below.

Meanwhile today at the Android mini-conference during the Linux Plumbers Conference was a presentation by Kalesh Singh of Google around the MGLRU performance on Android devices. The benchmark results there are simply outstanding and the numbers speak for themselves:

The Android MGLRU presentation from LPC 2022 is embedded below and there is also the slide deck for all the numbers.

As for the MGLRU prospects for Linux 6.1, Andrew Morton commented that he'd like to move the MGLRU patches to his "mm-stable" branch later this week. Though he has expressed some concern over the level of code review and that code commenting could be improved upon. He's hoping though that things will get pushed along. We'll see when the Linux 6.1 merge window opens up in October if MGLRU is ready for mainline.