From: SeongJae Park <sjpark@xxxxxxxxx> DAMON and DAMOS --------------- DAMON[1] is a framework for general data access monitoring of kernel subsystems. It provides best-effort high quality monitoring results while incurring only minimal and upper-bounded overhead, due to its practical overhead-accuracy tradeoff mechanism. On a production machine utilizing 70 GB memory, it can repeatedly scan accesses to the whole memory for every 5ms, while consuming only 1% single CPU time. On top of it, a data access pattern-oriented memory management engine called DAMON-based Operation Schemes (DAMOS) is implemented. It allows clients to implement their access pattern oriented memory management logic with very simple scheme descriptions. We implemented fine-grained access-aware THP and proactive reclamation using this engine in three lines of scheme and achieved remarkable improvements[2]. As of this writing (2021-05-28), the code is not in the mainline but available at its development tree[3], and regularly posted to LKML as patchsets[4,5,6]. Nevertheless, the code has already merged in the public Amazon Linux kernel trees[7,8], and all Amazon Linux users can use DAMON/DAMOS off the box. We are also supporting the two latest upstream LTS stable kernels[9,10]. Agenda ------ In this talk, I will briefly introduce DAMON/DAMOS and present how you can write a fine-grained data access pattern oriented lightweight kernel module on top of DAMON/DAMOS. With the talk, I will write an example module and evaluate its performance on live. A data access-aware proactive reclamation kernel module for production use will also introduced as a use case. After that, I will discuss my future plans for improving DAMON and improving other kernel subsystems using DAMON/DAMOS. [1] https://damonitor.github.io (https://damonitor.github.io/) [2] https://damonitor.github.io/doc/html/latest/vm/damon/eval.html [3] https://https://github.com/sjp38/linux/tree/damon/master (https://https//github.com/sjp38/linux/tree/damon/master) [4] https://lore.kernel.org/linux-mm/20210520075629.4332-1-sj38.park@xxxxxxxxx/ [5] https://lore.kernel.org/linux-mm/20201216084404.23183-1-sjpark@xxxxxxxxxx/ [6] https://lore.kernel.org/linux-mm/20201216094221.11898-1-sjpark@xxxxxxxxxx/ [7] https://github.com/amazonlinux/linux/tree/amazon-5.4.y/master/mm/damon [8] https://github.com/amazonlinux/linux/tree/amazon-5.10.y/master/mm/damon [9] https://github.com/sjp38/linux/tree/damon/for-v5.4.y [10] https://github.com/sjp38/linux/tree/damon/for-v5.10.y
