DAMO: Data Access Monitoring Operator

damo is a user space tool for DAMON. Using this, you can monitor the data access patterns of your system or workloads and do data access-aware memory management operations.

Official Repositories

Official git repos for damo are hosted on kernel.org and GitHub:

• kernel.org: https://git.kernel.org/pub/scm/linux/kernel/git/sj/damo.git
• GitHub: https://github.com/damonitor/damo

Demo Video

Please click the below thumbnail to show the short demo video. Note that the video is recorded in 2020, and hence not showing features added after the demo.

Getting Started

Follow below instructions and commands to monitor and visualize the access pattern of your workload.

$ # install damo using packaging systems listed above,
$ # or cloning the source repo and updating $PATH.
$ sudo damo start $(pidof <your workload>)
$ sudo damo report access
$ sudo damo record ongoing
$ sudo damo report heatmap --draw_range hottest

The second and last commands will show the access pattern of your workload, like below:

FAQs

What kernels are supported by damo?

damo provides three categories of commands,

• for controlling DAMON in kernel,
• for processing DAMON-generated outputs such as access monitoring output, and
• for misc helpers.

Commands not in the first category are independent to the kernel.

Commands of the first category depends on if DAMON features for the given command is available on the running kernel. Essential DAMON features are available on kernels that built with CONFIG_DAMON=y.

If the system is configured in a way that necessary DAMON features are not available, the damo commands will fail with messages informing the reason and how you can get help, like below.

$ sudo damo start

DAMON is not available on this system.  Ask help to your sysadmin or DAMON
community.

To ask help to DAMON community, you can
- send a mail to the mailing list (damon@lists.linux.dev),
- open a damo GitHub issue (https://github.com/damonitor/damo/issues), or
- send a mail to DAMON maintainer: sj@kernel.org

Follow the recommendation in the message for help. Again, note that only commands in the first category depend on the kernel.

To see if DAMON is available on your system without running such commands, damo report sysinfo can be used. If the output of the command shows DAMON version as <5.15, DAMON is not available on the system.

For example, on a system that DAMON is not available:

$ sudo damo report sysinfo
damo version: v3.1.5-29-gad48ac5b
kernel version: 6.19.0-rc6-mm-new-damon+
DAMON version: <5.15

On a system that DAMON is available:

$ sudo damo report sysinfo --print versions
damo version: v3.1.5-24-gfc8c0e51
kernel version: 6.19.0-rc6-mm-new-damon+
DAMON version: 6.19+

If you unsure if your kernel enables DAMON or how to enable DAMON on your kernel, please ask help to your kernel provider, or DAMON community.

Where can I get more detailed usage?

The below sections provide quick introductions for damo's major features. For more detailed usage, please refer to USAGE.md file.

What does the version numbers mean?

Nothing at all but indicate which version is more fresh. A higher version number means it is more recently released.

This also means that there is no special versions for hotfixes. Instead, all bug fixes and new features are released together in fast speed (nearly once per week) under the single version scheme. We also strive a high level of stability across all versions. Users are therefore recommended to use latest version always if possible. It is the only way to get all bug fixes and new features. If there is any problem at upgrading the version, please report an issue.

Will the features of damo be supported forever?

We try our best to make damo stable and doesn't introduce regressions to users. However, nothing goes forever. Sometimes, some features will be deprecated. Some features will have longer support more than others.

In short, features that documented on USAGE.md and not explicitly marked as experimental will be better supported, and provides at least three months of deprecation grace period. Within the grace period, users can ask extension of the support. Even after the grace period, please reach out to damo developers if that makes problem to your usage.

Detailed features deprecation process is documented at FEATURES_DEPRECATION_PROCESS.md. Schedules and status of deprecations are updated on FEATURES_DEPRECATION_SCHEDULE.md.

How can I participate in the development of damo?

Please refer to CONTRIBUTING file.

Quick Intro for Major Features

Below are quick introductions for damo's major features. For more detailed usage, please refer to USAGE.md file.

Snapshot Data Access Pattern

Below commands repeatedly get a snapshot of the access pattern of a program for every second.

$ git clone https://github.com/sjp38/masim
$ cd masim; make; ./masim ./configs/zigzag.cfg --silent &
$ sudo damo start --target_pid $(pidof masim)
$ sudo damo report access --repeat

The first two lines of the commands get an artificial memory access generator program and run it in the background. It will repeatedly access two 100 MiB-sized memory regions one by one. You can substitute this with your real workload.

The third line asks damo to start monitoring the access pattern of the process. Finally, the last line retries a snapshot of the monitoring results every second and show on terminal.

Recording Data Access Patterns

Below commands record memory access patterns of a program and save the monitoring results in damon.data file.

$ git clone https://github.com/sjp38/masim
$ cd masim; make; ./masim ./configs/zigzag.cfg --silent &
$ sudo damo record -o damon.data $(pidof masim)

The first two lines of the commands get an artificial memory access generator program and run it in the background. It will repeatedly access two 100 MiB-sized memory regions one by one. You can substitute this with your real workload. The last line asks damo to record the access pattern in damon.data file.

Visualizing Recorded Patterns

Below three commands visualize the recorded access patterns into five image files.

$ damo report heatmap --output access_pattern_heatmap.png --draw_range all
$ damo report wss --range 0 101 1 --plot wss_dist.png
$ damo report wss --range 0 101 1 --sortby time --plot wss_chron_change.png

The first command will create three files, namely access_pattern_heatmap.png, access_patern_heatmap.1.png, and access_pattern_heatmap.2.png.

• access_pattern_heatmap{,1,2}.png will show the data access pattern of three address ranges nearby stack, mmap()-ed region, and heat in heatmaps, which shows when (x-axis) what memory region (y-axis) is how frequently accessed (color).
• wss_dist.png will show the distribution of the working set size.
• wss_chron_change.png will show how the working set size has chronologically changed.

Those similarly made with other realistic workloads are available [1,2,3].

[1] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
[2] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
[3] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html

Data Access Pattern Aware Memory Management

Below command makes every memory region of size >=4K that hasn't accessed for

=60 seconds in your workload to be swapped out. By doing this, you can make your workload more memory efficient with only modest performance overhead.

$ sudo damo start --damos_access_rate 0 0 --damos_sz_region 4K max \
                    --damos_age 60s max --damos_action pageout \
                    --target_pid <pid of your workload>

Holistic Memory Usage Monitoring

You can also show access pattern heatmap, memory footprints, and hotspot functions of the system and/or workloads all at once in live, like below.