04cc7e4bf7
'Getting Started' document of DAMON says DAMON user-space tool, damo[1],
is using DAMON debugfs interface, and therefore it needs to ensure debugfs
is mounted. However, the latest version of the tool is using DAMON sysfs
interface. Moreover, DAMON debugfs interface is going to be deprecated as
announced by commit b18402726bd1 ("Docs/admin-guide/mm/damon/usage:
document DAMON sysfs interface").
This commit therefore update the document to tell readers about DAMON
sysfs interface dependency instead and never mention about debugfs
interface, which will be deprecated.
[1] https://github.com/awslabs/damo
Link: https://lkml.kernel.org/r/20220909202901.57977-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Yun Levi <ppbuk5246@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
128 lines
6.0 KiB
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128 lines
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.. SPDX-License-Identifier: GPL-2.0
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===============
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Getting Started
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===============
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This document briefly describes how you can use DAMON by demonstrating its
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default user space tool. Please note that this document describes only a part
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of its features for brevity. Please refer to the usage `doc
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<https://github.com/awslabs/damo/blob/next/USAGE.md>`_ of the tool for more
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details.
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Prerequisites
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=============
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Kernel
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------
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You should first ensure your system is running on a kernel built with
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``CONFIG_DAMON_*=y``.
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User Space Tool
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---------------
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For the demonstration, we will use the default user space tool for DAMON,
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called DAMON Operator (DAMO). It is available at
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https://github.com/awslabs/damo. The examples below assume that ``damo`` is on
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your ``$PATH``. It's not mandatory, though.
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Because DAMO is using the sysfs interface (refer to :doc:`usage` for the
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detail) of DAMON, you should ensure :doc:`sysfs </filesystems/sysfs>` is
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mounted.
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Recording Data Access Patterns
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==============================
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The commands below record the memory access patterns of a program and save the
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monitoring results to a file. ::
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$ git clone https://github.com/sjp38/masim
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$ cd masim; make; ./masim ./configs/zigzag.cfg &
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$ sudo damo record -o damon.data $(pidof masim)
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The first two lines of the commands download an artificial memory access
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generator program and run it in the background. The generator will repeatedly
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access two 100 MiB sized memory regions one by one. You can substitute this
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with your real workload. The last line asks ``damo`` to record the access
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pattern in the ``damon.data`` file.
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Visualizing Recorded Patterns
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=============================
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You can visualize the pattern in a heatmap, showing which memory region
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(x-axis) got accessed when (y-axis) and how frequently (number).::
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$ sudo damo report heats --heatmap stdout
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22222222222222222222222222222222222222211111111111111111111111111111111111111100
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44444444444444444444444444444444444444434444444444444444444444444444444444443200
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44444444444444444444444444444444444444433444444444444444444444444444444444444200
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33333333333333333333333333333333333333344555555555555555555555555555555555555200
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33333333333333333333333333333333333344444444444444444444444444444444444444444200
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22222222222222222222222222222222222223355555555555555555555555555555555555555200
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00000000000000000000000000000000000000288888888888888888888888888888888888888400
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00000000000000000000000000000000000000288888888888888888888888888888888888888400
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33333333333333333333333333333333333333355555555555555555555555555555555555555200
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88888888888888888888888888888888888888600000000000000000000000000000000000000000
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88888888888888888888888888888888888888600000000000000000000000000000000000000000
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33333333333333333333333333333333333333444444444444444444444444444444444444443200
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00000000000000000000000000000000000000288888888888888888888888888888888888888400
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[...]
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# access_frequency: 0 1 2 3 4 5 6 7 8 9
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# x-axis: space (139728247021568-139728453431248: 196.848 MiB)
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# y-axis: time (15256597248362-15326899978162: 1 m 10.303 s)
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# resolution: 80x40 (2.461 MiB and 1.758 s for each character)
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You can also visualize the distribution of the working set size, sorted by the
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size.::
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$ sudo damo report wss --range 0 101 10
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# <percentile> <wss>
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# target_id 18446632103789443072
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# avr: 107.708 MiB
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0 0 B | |
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10 95.328 MiB |**************************** |
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20 95.332 MiB |**************************** |
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30 95.340 MiB |**************************** |
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40 95.387 MiB |**************************** |
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50 95.387 MiB |**************************** |
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60 95.398 MiB |**************************** |
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70 95.398 MiB |**************************** |
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80 95.504 MiB |**************************** |
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90 190.703 MiB |********************************************************* |
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100 196.875 MiB |***********************************************************|
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Using ``--sortby`` option with the above command, you can show how the working
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set size has chronologically changed.::
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$ sudo damo report wss --range 0 101 10 --sortby time
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# <percentile> <wss>
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# target_id 18446632103789443072
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# avr: 107.708 MiB
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0 3.051 MiB | |
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10 190.703 MiB |***********************************************************|
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20 95.336 MiB |***************************** |
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30 95.328 MiB |***************************** |
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40 95.387 MiB |***************************** |
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50 95.332 MiB |***************************** |
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60 95.320 MiB |***************************** |
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70 95.398 MiB |***************************** |
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80 95.398 MiB |***************************** |
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90 95.340 MiB |***************************** |
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100 95.398 MiB |***************************** |
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Data Access Pattern Aware Memory Management
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===========================================
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Below three commands make every memory region of size >=4K that doesn't
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accessed for >=60 seconds in your workload to be swapped out. ::
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$ echo "#min-size max-size min-acc max-acc min-age max-age action" > test_scheme
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$ echo "4K max 0 0 60s max pageout" >> test_scheme
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$ damo schemes -c test_scheme <pid of your workload>
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