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Docs/admin-guide/mm/damon/start: simplify the content
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Information in 'TL; DR' section of 'Getting Started' is duplicated in
other parts of the doc.  It is also asking readers to visit the access
pattern visualizations gallery web site to show the results of example
visualization commands, while the users of the commands can use terminal
output.

To make the doc simple, this removes the duplicated 'TL; DR' section and
replaces the visualization example commands with versions using terminal
outputs.

Link: https://lkml.kernel.org/r/20211022090311.3856-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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SeongJae Park authored and Linus Torvalds committed Nov 6, 2021
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113 changes: 60 additions & 53 deletions Documentation/admin-guide/mm/damon/start.rst
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Expand Up @@ -11,38 +11,6 @@ of its features for brevity. Please refer to the usage `doc
details.


TL; DR
======

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

# # build the kernel with CONFIG_DAMON_*=y, install it, and reboot
# mount -t debugfs none /sys/kernel/debug/
# git clone https://github.com/awslabs/damo
# ./damo/damo record $(pidof <your workload>)
# ./damo/damo report heats --heatmap stdout

The final command draws the access heatmap of ``<your workload>``. The heatmap
shows which memory region (x-axis) is accessed when (y-axis) and how frequently
(number; the higher the more accesses have been observed). ::

111111111111111111111111111111111111111111111111111111110000
111121111111111111111111111111211111111111111111111111110000
000000000000000000000000000000000000000000000000001555552000
000000000000000000000000000000000000000000000222223555552000
000000000000000000000000000000000000000011111677775000000000
000000000000000000000000000000000000000488888000000000000000
000000000000000000000000000000000177888400000000000000000000
000000000000000000000000000046666522222100000000000000000000
000000000000000000000014444344444300000000000000000000000000
000000000000000002222245555510000000000000000000000000000000
# access_frequency: 0 1 2 3 4 5 6 7 8 9
# x-axis: space (140286319947776-140286426374096: 101.496 MiB)
# y-axis: time (605442256436361-605479951866441: 37.695430s)
# resolution: 60x10 (1.692 MiB and 3.770s for each character)


Prerequisites
=============

Expand Down Expand Up @@ -93,22 +61,66 @@ pattern in the ``damon.data`` file.
Visualizing Recorded Patterns
=============================

The following three commands visualize the recorded access patterns and save
the results as separate image files. ::

$ sudo damo report heats --heatmap access_pattern_heatmap.png
$ sudo damo report wss --range 0 101 1 --plot wss_dist.png
$ sudo damo report wss --range 0 101 1 --sortby time --plot wss_chron_change.png

- ``access_pattern_heatmap.png`` will visualize the data access pattern in a
heatmap, showing which memory region (y-axis) got accessed when (x-axis)
and how frequently (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.

You can view the visualizations of this example workload at [1]_.
Visualizations of other realistic workloads are available at [2]_ [3]_ [4]_.
You can visualize the pattern in a heatmap, showing which memory region
(x-axis) got accessed when (y-axis) and how frequently (number).::

$ sudo damo report heats --heatmap stdout
22222222222222222222222222222222222222211111111111111111111111111111111111111100
44444444444444444444444444444444444444434444444444444444444444444444444444443200
44444444444444444444444444444444444444433444444444444444444444444444444444444200
33333333333333333333333333333333333333344555555555555555555555555555555555555200
33333333333333333333333333333333333344444444444444444444444444444444444444444200
22222222222222222222222222222222222223355555555555555555555555555555555555555200
00000000000000000000000000000000000000288888888888888888888888888888888888888400
00000000000000000000000000000000000000288888888888888888888888888888888888888400
33333333333333333333333333333333333333355555555555555555555555555555555555555200
88888888888888888888888888888888888888600000000000000000000000000000000000000000
88888888888888888888888888888888888888600000000000000000000000000000000000000000
33333333333333333333333333333333333333444444444444444444444444444444444444443200
00000000000000000000000000000000000000288888888888888888888888888888888888888400
[...]
# access_frequency: 0 1 2 3 4 5 6 7 8 9
# x-axis: space (139728247021568-139728453431248: 196.848 MiB)
# y-axis: time (15256597248362-15326899978162: 1 m 10.303 s)
# resolution: 80x40 (2.461 MiB and 1.758 s for each character)

You can also visualize the distribution of the working set size, sorted by the
size.::

$ sudo damo report wss --range 0 101 10
# <percentile> <wss>
# target_id 18446632103789443072
# avr: 107.708 MiB
0 0 B | |
10 95.328 MiB |**************************** |
20 95.332 MiB |**************************** |
30 95.340 MiB |**************************** |
40 95.387 MiB |**************************** |
50 95.387 MiB |**************************** |
60 95.398 MiB |**************************** |
70 95.398 MiB |**************************** |
80 95.504 MiB |**************************** |
90 190.703 MiB |********************************************************* |
100 196.875 MiB |***********************************************************|

Using ``--sortby`` option with the above command, you can show how the working
set size has chronologically changed.::

$ sudo damo report wss --range 0 101 10 --sortby time
# <percentile> <wss>
# target_id 18446632103789443072
# avr: 107.708 MiB
0 3.051 MiB | |
10 190.703 MiB |***********************************************************|
20 95.336 MiB |***************************** |
30 95.328 MiB |***************************** |
40 95.387 MiB |***************************** |
50 95.332 MiB |***************************** |
60 95.320 MiB |***************************** |
70 95.398 MiB |***************************** |
80 95.398 MiB |***************************** |
90 95.340 MiB |***************************** |
100 95.398 MiB |***************************** |


Data Access Pattern Aware Memory Management
Expand All @@ -120,8 +132,3 @@ 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" > test_scheme
$ echo "4K max 0 0 60s max pageout" >> test_scheme
$ damo schemes -c test_scheme <pid of your workload>

.. [1] https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/start.html#visualizing-recorded-patterns
.. [2] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
.. [3] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
.. [4] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html

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