Amazon's DAMON Merged Into Linux 5.15 For Data Access Monitoring Framework

Written by Michael Larabel in Linux Kernel on 8 September 2021 at 04:22 PM EDT. 5 Comments
The DAMON kernel functionality developed by Amazon engineers has successfully landed in the Linux 5.15 tree.

As part of the 147 patches herded into the kernel today by Andrew Morton, the most notable addition is the merging of the DAMON functionality.

Since the start of 2020 there have been patches out of Amazon for DAMON as a Linux kernel addition around monitoring data accesses. DAMON is designed for a variety of use-cases from behavior analysis to assist in debugging to dealing with over-committed systems. One of the areas recently receiving some attention and for building on DAMON moving forward is proactive reclamation of system memory.

After the DAMON code went through around three dozen rounds of review over the past year and a half, it was merged today to mainline.

Today's landing shouldn't come as a surprise as a month ago Andrew Morton indicated he would take it via his patch collection for 5.15.
DAMON is a data access monitoring framework subsystem for the Linux kernel. The core mechanisms of DAMON called 'region based sampling' and 'adaptive regions adjustment' make it

- accurate (The monitored information is useful for DRAM level memory management. It might not appropriate for Cache-level accuracy, though.),
- light-weight (The monitoring overhead is low enough to be applied online while making no impact on the performance of the target workloads.), and
- scalable (the upper-bound of the instrumentation overhead is controllable regardless of the size of target workloads.).

Using this framework, therefore, the kernel's core memory management mechanisms such as reclamation and THP can be optimized for better memory management. The experimental memory management optimization works that incurring high instrumentation overhead will be able to have another try. In user space, meanwhile, users who have some special workloads will be able to write personalized tools or applications for deeper understanding and specialized optimizations of their systems.

The core DAMON code is just under four thousand lines of code while it will be very interesting moving forward to see what new DAMON-based solutions may come to the kernel. More details on DAMON via the documentation.
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