Hi all, Thanks to the discussions and feedback that we received last year from the LSF/MM/BPF 2023's DAMON updates and future plans session[1], DAMON made many advances and yet more future plans. I'd like to again share/discuss the followup changes and status we made so far after the last year's session, and the future development plans on LSF/MM/BPF 2024. A few topics would be shared, including below. User Aims-oriented DAMOS Self-tuning ------------------------------------ I shared "feedback-based quota auto tuning" as the top priority item for 2023 in last year's session. Fortunately it made some progress. A simple feedback loop-based quota tuning and user feedback interface have been implemented and merged into the mainline from v6.8-rc1. By the time of LSF/MM/BPF 2024, hopefully the remaining part of the initial idea, specifically making DAMON feeds itself, will be implemented and merged in the mm tree. I'd like to share the implementation details, discuss remaining rooms for improvements, and find future extension opportunities. Hopefully DAMON monitoring parameters auto-tuning would be one of the future works to consider. DAMON-based Tiered Memory Management ------------------------------------ I'm personally not working on this topic directly, but apparently a few folks are exploring DAMON usage for tiered memory management. Some academic papers[2,3] exploring the opportunity have been published. I shared a rough RFC idea[4] of it based on the self-tuning in November 2023. Recently SK hynix has also adopted DAMON for their CXL-based tiered memory management solution[5], and sent patches for their work[6]. I'd like to provide a summary of the ongoing works and updates on my idea. Hopefully early proof-of-concepts level implementation of my idea would be shared in the session. Access/Contiguity-aware Memory Auto-scaling ------------------------------------------- This is a new idea which was not discussed in last year's LSF/MM/BPF. The main purpose is to implement an access-aware, efficient, reliable, and simple to use memory over-subscribed VM guest kernels. Specifically, it will steal guest memory based on access patterns in a contiguity-aware manner and report those to the host as free to use. The PSI-based stealing aggressiveness auto-tuning may be used. It will also apply a 'struct page' overhead reduction mechanism to the stolen memory. We're currently thinking about memory hotplugging and vmemmap remapping as candidate mechanisms. For simple usage, the interface will be similar to that of virtio-balloon, which is widely adopted. The first version of the more detailed idea[7] has been shared before. Because it is still at a pure idea level, not much progress until LSF/MM/BPF is expected. This item would be primarily for the future plans part. That said, at least a second version of the design will be shared before. Also hopefully early proof-of-concepts level implementation or some test results will be shared. Since this is expected to be more for future plans than status update, I hope to have more discussions for getting design level concerns and possible collaboration chances. Misc ---- If time allows, I would be able to cover more follow ups for items that I shared as the future plans, and the feedback/questions I received from the last year's session. - Merging DAMON user-space tool in the tree - DAMON documentation improvements - Write-only monitoring - THP memory footprint reduction - DAMON-based working set size report - In production DAMON usages [1] https://lwn.net/Articles/931769/ [2] https://arxiv.org/abs/2302.09468 [3] https://dl.acm.org/doi/10.1145/3600006.3613167 [4] https://lore.kernel.org/damon/20231112195602.61525-1-sj@xxxxxxxxxx/ [5] https://github.com/skhynix/hmsdk/releases/tag/hmsdk-v2.0 [6] https://lore.kernel.org/r/20240115045253.1775-1-honggyu.kim@xxxxxx [7] https://lore.kernel.org/damon/20231112195114.61474-1-sj@xxxxxxxxxx/ Thanks, SJ
