This document briefly describes how you can use DAMON by demonstrating its default user space tool. Please note that this document describes only a part of its features for brevity. Please refer to Detailed Usages for more details.
Follow below 5 commands to monitor and visualize the access pattern of your workload.
$ git clone https://github.com/sjp38/linux -b damon/master /* build the kernel with CONFIG_DAMON=y, install, reboot */ $ mount -t debugfs none /sys/kernel/debug/ $ cd linux/tools/damon $ ./damo record $(pidof <your workload>) $ ./damo report heats --heatmap access_pattern.png
You should first ensure your system is running on a kernel built with
CONFIG_DAMON. If the value is set to
m, load the module first:
# modprobe damon
User Space Tool¶
For the demonstration, we will use the default user space tool for DAMON,
called DAMON Operator (DAMO). It is located at
tools/damon/damo of the
kernel source tree. For brevity, below examples assume you set
point it. It’s not mandatory, though.
Because DAMO is using the debugfs interface (refer to Detailed Usages for the detail) of DAMON, you should ensure debugfs is mounted. Mount it manually as below:
# mount -t debugfs none /sys/kernel/debug/
or append below line to your
/etc/fstab file so that your system can
automatically mount debugfs from next booting:
debugfs /sys/kernel/debug debugfs defaults 0 0
Recording Data Access Patterns¶
Below commands record memory access pattern of a program and save the monitoring results in a file.
$ git clone https://github.com/sjp38/masim $ cd masim; make; ./masim ./configs/zigzag.cfg & $ sudo damo record -o damon.data $(pidof masim)
The first two lines of the commands get an artificial memory access generator
program and runs 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
Visualizing Recorded Patterns¶
Below three commands visualize the recorded access patterns into three image files.
$ damo report heats --heatmap access_pattern_heatmap.png $ 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
access_pattern_heatmap.pngwill show the data access pattern in a heatmap, which shows when (x-axis) what memory region (y-axis) is how frequently accessed (color).
wss_dist.pngwill show the distribution of the working set size.
wss_chron_change.pngwill show how the working set size has chronologically changed.
Data Access Pattern Aware Memory Management¶
Below three commands make every memory region of size >=4K that doesn’t accessed for >=60 seconds in your workload to be swapped out.
$ echo "#min-size max-size min-acc max-acc min-age max-age action" > scheme $ echo "4K max 0 0 60s max pageout" >> scheme $ damo schemes -c my_thp_scheme <pid of your workload>