165 lines
7.8 KiB
ReStructuredText
165 lines
7.8 KiB
ReStructuredText
.. 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/damonitor/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/damonitor/damo. The examples below assume that ``damo`` is on
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your ``$PATH``. It's not mandatory, though.
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Because DAMO is using the sysfs interface (refer to :doc:`usage` for the
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detail) of DAMON, you should ensure :doc:`sysfs </filesystems/sysfs>` is
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mounted.
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Snapshot Data Access Patterns
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=============================
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The commands below show the memory access pattern of a program at the moment of
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the execution. ::
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$ git clone https://github.com/sjp38/masim; cd masim; make
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$ sudo damo start "./masim ./configs/stairs.cfg --quiet"
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$ sudo ./damo show
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0 addr [85.541 TiB , 85.541 TiB ) (57.707 MiB ) access 0 % age 10.400 s
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1 addr [85.541 TiB , 85.542 TiB ) (413.285 MiB) access 0 % age 11.400 s
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2 addr [127.649 TiB , 127.649 TiB) (57.500 MiB ) access 0 % age 1.600 s
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3 addr [127.649 TiB , 127.649 TiB) (32.500 MiB ) access 0 % age 500 ms
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4 addr [127.649 TiB , 127.649 TiB) (9.535 MiB ) access 100 % age 300 ms
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5 addr [127.649 TiB , 127.649 TiB) (8.000 KiB ) access 60 % age 0 ns
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6 addr [127.649 TiB , 127.649 TiB) (6.926 MiB ) access 0 % age 1 s
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7 addr [127.998 TiB , 127.998 TiB) (120.000 KiB) access 0 % age 11.100 s
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8 addr [127.998 TiB , 127.998 TiB) (8.000 KiB ) access 40 % age 100 ms
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9 addr [127.998 TiB , 127.998 TiB) (4.000 KiB ) access 0 % age 11 s
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total size: 577.590 MiB
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$ sudo ./damo stop
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The first command of the above example downloads and builds an artificial
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memory access generator program called ``masim``. The second command asks DAMO
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to execute the artificial generator process start via the given command and
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make DAMON monitors the generator process. The third command retrieves the
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current snapshot of the monitored access pattern of the process from DAMON and
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shows the pattern in a human readable format.
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Each line of the output shows which virtual address range (``addr [XX, XX)``)
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of the process is how frequently (``access XX %``) accessed for how long time
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(``age XX``). For example, the fifth region of ~9 MiB size is being most
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frequently accessed for last 300 milliseconds. Finally, the fourth command
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stops DAMON.
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Note that DAMON can monitor not only virtual address spaces but multiple types
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of address spaces including the physical address space.
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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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$ ./masim ./configs/zigzag.cfg &
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$ sudo damo record -o damon.data $(pidof masim)
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The line of the commands run the artificial memory access
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generator program again. The generator will repeatedly
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access two 100 MiB sized memory regions one by one. You can substitute this
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with your real workload. The last line asks ``damo`` to record the access
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pattern in the ``damon.data`` file.
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Visualizing Recorded Patterns
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=============================
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You can visualize the pattern in a heatmap, showing which memory region
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(x-axis) got accessed when (y-axis) and how frequently (number).::
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$ 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 command makes every memory region of size >=4K that has not accessed for
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>=60 seconds in your workload to be swapped out. ::
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$ sudo damo schemes --damos_access_rate 0 0 --damos_sz_region 4K max \
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--damos_age 60s max --damos_action pageout \
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<pid of your workload>
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