1 .. SPDX-License-Identifier: GPL-2.0
7 This document briefly describes how you can use DAMON by demonstrating its
8 default user space tool. Please note that this document describes only a part
9 of its features for brevity. Please refer to :doc:`usage` for more details.
15 Follow the commands below to monitor and visualize the memory access pattern of
18 # # build the kernel with CONFIG_DAMON_*=y, install it, and reboot
19 # mount -t debugfs none /sys/kernel/debug/
20 # git clone https://github.com/awslabs/damo
21 # ./damo/damo record $(pidof <your workload>)
22 # ./damo/damo report heat --plot_ascii
24 The final command draws the access heatmap of ``<your workload>``. The heatmap
25 shows which memory region (x-axis) is accessed when (y-axis) and how frequently
26 (number; the higher the more accesses have been observed). ::
28 111111111111111111111111111111111111111111111111111111110000
29 111121111111111111111111111111211111111111111111111111110000
30 000000000000000000000000000000000000000000000000001555552000
31 000000000000000000000000000000000000000000000222223555552000
32 000000000000000000000000000000000000000011111677775000000000
33 000000000000000000000000000000000000000488888000000000000000
34 000000000000000000000000000000000177888400000000000000000000
35 000000000000000000000000000046666522222100000000000000000000
36 000000000000000000000014444344444300000000000000000000000000
37 000000000000000002222245555510000000000000000000000000000000
38 # access_frequency: 0 1 2 3 4 5 6 7 8 9
39 # x-axis: space (140286319947776-140286426374096: 101.496 MiB)
40 # y-axis: time (605442256436361-605479951866441: 37.695430s)
41 # resolution: 60x10 (1.692 MiB and 3.770s for each character)
50 You should first ensure your system is running on a kernel built with
57 For the demonstration, we will use the default user space tool for DAMON,
58 called DAMON Operator (DAMO). It is available at
59 https://github.com/awslabs/damo. The examples below assume that ``damo`` is on
60 your ``$PATH``. It's not mandatory, though.
62 Because DAMO is using the debugfs interface (refer to :doc:`usage` for the
63 detail) of DAMON, you should ensure debugfs is mounted. Mount it manually as
66 # mount -t debugfs none /sys/kernel/debug/
68 or append the following line to your ``/etc/fstab`` file so that your system
69 can automatically mount debugfs upon booting::
71 debugfs /sys/kernel/debug debugfs defaults 0 0
74 Recording Data Access Patterns
75 ==============================
77 The commands below record the memory access patterns of a program and save the
78 monitoring results to a file. ::
80 $ git clone https://github.com/sjp38/masim
81 $ cd masim; make; ./masim ./configs/zigzag.cfg &
82 $ sudo damo record -o damon.data $(pidof masim)
84 The first two lines of the commands download an artificial memory access
85 generator program and run it in the background. The generator will repeatedly
86 access two 100 MiB sized memory regions one by one. You can substitute this
87 with your real workload. The last line asks ``damo`` to record the access
88 pattern in the ``damon.data`` file.
91 Visualizing Recorded Patterns
92 =============================
94 The following three commands visualize the recorded access patterns and save
95 the results as separate image files. ::
97 $ damo report heats --heatmap access_pattern_heatmap.png
98 $ damo report wss --range 0 101 1 --plot wss_dist.png
99 $ damo report wss --range 0 101 1 --sortby time --plot wss_chron_change.png
101 - ``access_pattern_heatmap.png`` will visualize the data access pattern in a
102 heatmap, showing which memory region (y-axis) got accessed when (x-axis)
103 and how frequently (color).
104 - ``wss_dist.png`` will show the distribution of the working set size.
105 - ``wss_chron_change.png`` will show how the working set size has
106 chronologically changed.
108 You can view the visualizations of this example workload at [1]_.
109 Visualizations of other realistic workloads are available at [2]_ [3]_ [4]_.
112 Data Access Pattern Aware Memory Management
113 ===========================================
115 Below three commands make every memory region of size >=4K that doesn't
116 accessed for >=60 seconds in your workload to be swapped out. ::
118 $ echo "#min-size max-size min-acc max-acc min-age max-age action" > scheme
119 $ echo "4K max 0 0 60s max pageout" >> scheme
120 $ damo schemes -c my_thp_scheme <pid of your workload>
122 .. [1] https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/start.html#visualizing-recorded-patterns
123 .. [2] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
124 .. [3] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
125 .. [4] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html