Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

5 files changed, 1524 insertions, 0 deletions

diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst
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@@ -0,0 +1,17 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+DAMON: Data Access MONitor
+==========================
+
+:doc:`DAMON </mm/damon/index>` allows light-weight data access monitoring.
+Using DAMON, users can analyze the memory access patterns of their systems and
+optimize those.
+
+.. toctree::
+   :maxdepth: 2
+
+   start
+   usage
+   reclaim
+   lru_sort
diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst
new file mode 100644
index 0000000000..7b0775d281
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/lru_sort.rst
@@ -0,0 +1,294 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============================
+DAMON-based LRU-lists Sorting
+=============================
+
+DAMON-based LRU-lists Sorting (DAMON_LRU_SORT) is a static kernel module that
+aimed to be used for proactive and lightweight data access pattern based
+(de)prioritization of pages on their LRU-lists for making LRU-lists a more
+trusworthy data access pattern source.
+
+Where Proactive LRU-lists Sorting is Required?
+==============================================
+
+As page-granularity access checking overhead could be significant on huge
+systems, LRU lists are normally not proactively sorted but partially and
+reactively sorted for special events including specific user requests, system
+calls and memory pressure.  As a result, LRU lists are sometimes not so
+perfectly prepared to be used as a trustworthy access pattern source for some
+situations including reclamation target pages selection under sudden memory
+pressure.
+
+Because DAMON can identify access patterns of best-effort accuracy while
+inducing only user-specified range of overhead, proactively running
+DAMON_LRU_SORT could be helpful for making LRU lists more trustworthy access
+pattern source with low and controlled overhead.
+
+How It Works?
+=============
+
+DAMON_LRU_SORT finds hot pages (pages of memory regions that showing access
+rates that higher than a user-specified threshold) and cold pages (pages of
+memory regions that showing no access for a time that longer than a
+user-specified threshold) using DAMON, and prioritizes hot pages while
+deprioritizing cold pages on their LRU-lists.  To avoid it consuming too much
+CPU for the prioritizations, a CPU time usage limit can be configured.  Under
+the limit, it prioritizes and deprioritizes more hot and cold pages first,
+respectively.  System administrators can also configure under what situation
+this scheme should automatically activated and deactivated with three memory
+pressure watermarks.
+
+Its default parameters for hotness/coldness thresholds and CPU quota limit are
+conservatively chosen.  That is, the module under its default parameters could
+be widely used without harm for common situations while providing a level of
+benefits for systems having clear hot/cold access patterns under memory
+pressure while consuming only a limited small portion of CPU time.
+
+Interface: Module Parameters
+============================
+
+To use this feature, you should first ensure your system is running on a kernel
+that is built with ``CONFIG_DAMON_LRU_SORT=y``.
+
+To let sysadmins enable or disable it and tune for the given system,
+DAMON_LRU_SORT utilizes module parameters.  That is, you can put
+``damon_lru_sort.<parameter>=<value>`` on the kernel boot command line or write
+proper values to ``/sys/module/damon_lru_sort/parameters/<parameter>`` files.
+
+Below are the description of each parameter.
+
+enabled
+-------
+
+Enable or disable DAMON_LRU_SORT.
+
+You can enable DAMON_LRU_SORT by setting the value of this parameter as ``Y``.
+Setting it as ``N`` disables DAMON_LRU_SORT.  Note that DAMON_LRU_SORT could do
+no real monitoring and LRU-lists sorting due to the watermarks-based activation
+condition.  Refer to below descriptions for the watermarks parameter for this.
+
+commit_inputs
+-------------
+
+Make DAMON_LRU_SORT reads the input parameters again, except ``enabled``.
+
+Input parameters that updated while DAMON_LRU_SORT is running are not applied
+by default.  Once this parameter is set as ``Y``, DAMON_LRU_SORT reads values
+of parametrs except ``enabled`` again.  Once the re-reading is done, this
+parameter is set as ``N``.  If invalid parameters are found while the
+re-reading, DAMON_LRU_SORT will be disabled.
+
+hot_thres_access_freq
+---------------------
+
+Access frequency threshold for hot memory regions identification in permil.
+
+If a memory region is accessed in frequency of this or higher, DAMON_LRU_SORT
+identifies the region as hot, and mark it as accessed on the LRU list, so that
+it could not be reclaimed under memory pressure.  50% by default.
+
+cold_min_age
+------------
+
+Time threshold for cold memory regions identification in microseconds.
+
+If a memory region is not accessed for this or longer time, DAMON_LRU_SORT
+identifies the region as cold, and mark it as unaccessed on the LRU list, so
+that it could be reclaimed first under memory pressure.  120 seconds by
+default.
+
+quota_ms
+--------
+
+Limit of time for trying the LRU lists sorting in milliseconds.
+
+DAMON_LRU_SORT tries to use only up to this time within a time window
+(quota_reset_interval_ms) for trying LRU lists sorting.  This can be used
+for limiting CPU consumption of DAMON_LRU_SORT.  If the value is zero, the
+limit is disabled.
+
+10 ms by default.
+
+quota_reset_interval_ms
+-----------------------
+
+The time quota charge reset interval in milliseconds.
+
+The charge reset interval for the quota of time (quota_ms).  That is,
+DAMON_LRU_SORT does not try LRU-lists sorting for more than quota_ms
+milliseconds or quota_sz bytes within quota_reset_interval_ms milliseconds.
+
+1 second by default.
+
+wmarks_interval
+---------------
+
+The watermarks check time interval in microseconds.
+
+Minimal time to wait before checking the watermarks, when DAMON_LRU_SORT is
+enabled but inactive due to its watermarks rule.  5 seconds by default.
+
+wmarks_high
+-----------
+
+Free memory rate (per thousand) for the high watermark.
+
+If free memory of the system in bytes per thousand bytes is higher than this,
+DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the
+watermarks.  200 (20%) by default.
+
+wmarks_mid
+----------
+
+Free memory rate (per thousand) for the middle watermark.
+
+If free memory of the system in bytes per thousand bytes is between this and
+the low watermark, DAMON_LRU_SORT becomes active, so starts the monitoring and
+the LRU-lists sorting.  150 (15%) by default.
+
+wmarks_low
+----------
+
+Free memory rate (per thousand) for the low watermark.
+
+If free memory of the system in bytes per thousand bytes is lower than this,
+DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the
+watermarks.  50 (5%) by default.
+
+sample_interval
+---------------
+
+Sampling interval for the monitoring in microseconds.
+
+The sampling interval of DAMON for the cold memory monitoring.  Please refer to
+the DAMON documentation (:doc:`usage`) for more detail.  5ms by default.
+
+aggr_interval
+-------------
+
+Aggregation interval for the monitoring in microseconds.
+
+The aggregation interval of DAMON for the cold memory monitoring.  Please
+refer to the DAMON documentation (:doc:`usage`) for more detail.  100ms by
+default.
+
+min_nr_regions
+--------------
+
+Minimum number of monitoring regions.
+
+The minimal number of monitoring regions of DAMON for the cold memory
+monitoring.  This can be used to set lower-bound of the monitoring quality.
+But, setting this too high could result in increased monitoring overhead.
+Please refer to the DAMON documentation (:doc:`usage`) for more detail.  10 by
+default.
+
+max_nr_regions
+--------------
+
+Maximum number of monitoring regions.
+
+The maximum number of monitoring regions of DAMON for the cold memory
+monitoring.  This can be used to set upper-bound of the monitoring overhead.
+However, setting this too low could result in bad monitoring quality.  Please
+refer to the DAMON documentation (:doc:`usage`) for more detail.  1000 by
+defaults.
+
+monitor_region_start
+--------------------
+
+Start of target memory region in physical address.
+
+The start physical address of memory region that DAMON_LRU_SORT will do work
+against.  By default, biggest System RAM is used as the region.
+
+monitor_region_end
+------------------
+
+End of target memory region in physical address.
+
+The end physical address of memory region that DAMON_LRU_SORT will do work
+against.  By default, biggest System RAM is used as the region.
+
+kdamond_pid
+-----------
+
+PID of the DAMON thread.
+
+If DAMON_LRU_SORT is enabled, this becomes the PID of the worker thread.  Else,
+-1.
+
+nr_lru_sort_tried_hot_regions
+-----------------------------
+
+Number of hot memory regions that tried to be LRU-sorted.
+
+bytes_lru_sort_tried_hot_regions
+--------------------------------
+
+Total bytes of hot memory regions that tried to be LRU-sorted.
+
+nr_lru_sorted_hot_regions
+-------------------------
+
+Number of hot memory regions that successfully be LRU-sorted.
+
+bytes_lru_sorted_hot_regions
+----------------------------
+
+Total bytes of hot memory regions that successfully be LRU-sorted.
+
+nr_hot_quota_exceeds
+--------------------
+
+Number of times that the time quota limit for hot regions have exceeded.
+
+nr_lru_sort_tried_cold_regions
+------------------------------
+
+Number of cold memory regions that tried to be LRU-sorted.
+
+bytes_lru_sort_tried_cold_regions
+---------------------------------
+
+Total bytes of cold memory regions that tried to be LRU-sorted.
+
+nr_lru_sorted_cold_regions
+--------------------------
+
+Number of cold memory regions that successfully be LRU-sorted.
+
+bytes_lru_sorted_cold_regions
+-----------------------------
+
+Total bytes of cold memory regions that successfully be LRU-sorted.
+
+nr_cold_quota_exceeds
+---------------------
+
+Number of times that the time quota limit for cold regions have exceeded.
+
+Example
+=======
+
+Below runtime example commands make DAMON_LRU_SORT to find memory regions
+having >=50% access frequency and LRU-prioritize while LRU-deprioritizing
+memory regions that not accessed for 120 seconds.  The prioritization and
+deprioritization is limited to be done using only up to 1% CPU time to avoid
+DAMON_LRU_SORT consuming too much CPU time for the (de)prioritization.  It also
+asks DAMON_LRU_SORT to do nothing if the system's free memory rate is more than
+50%, but start the real works if it becomes lower than 40%.  If DAMON_RECLAIM
+doesn't make progress and therefore the free memory rate becomes lower than
+20%, it asks DAMON_LRU_SORT to do nothing again, so that we can fall back to
+the LRU-list based page granularity reclamation. ::
+
+    # cd /sys/module/damon_lru_sort/parameters
+    # echo 500 > hot_thres_access_freq
+    # echo 120000000 > cold_min_age
+    # echo 10 > quota_ms
+    # echo 1000 > quota_reset_interval_ms
+    # echo 500 > wmarks_high
+    # echo 400 > wmarks_mid
+    # echo 200 > wmarks_low
+    # echo Y > enabled
diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst
new file mode 100644
index 0000000000..343e25b252
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/reclaim.rst
@@ -0,0 +1,274 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================
+DAMON-based Reclamation
+=======================
+
+DAMON-based Reclamation (DAMON_RECLAIM) is a static kernel module that aimed to
+be used for proactive and lightweight reclamation under light memory pressure.
+It doesn't aim to replace the LRU-list based page_granularity reclamation, but
+to be selectively used for different level of memory pressure and requirements.
+
+Where Proactive Reclamation is Required?
+========================================
+
+On general memory over-committed systems, proactively reclaiming cold pages
+helps saving memory and reducing latency spikes that incurred by the direct
+reclaim of the process or CPU consumption of kswapd, while incurring only
+minimal performance degradation [1]_ [2]_ .
+
+Free Pages Reporting [3]_ based memory over-commit virtualization systems are
+good example of the cases.  In such systems, the guest VMs reports their free
+memory to host, and the host reallocates the reported memory to other guests.
+As a result, the memory of the systems are fully utilized.  However, the
+guests could be not so memory-frugal, mainly because some kernel subsystems and
+user-space applications are designed to use as much memory as available.  Then,
+guests could report only small amount of memory as free to host, results in
+memory utilization drop of the systems.  Running the proactive reclamation in
+guests could mitigate this problem.
+
+How It Works?
+=============
+
+DAMON_RECLAIM finds memory regions that didn't accessed for specific time
+duration and page out.  To avoid it consuming too much CPU for the paging out
+operation, a speed limit can be configured.  Under the speed limit, it pages
+out memory regions that didn't accessed longer time first.  System
+administrators can also configure under what situation this scheme should
+automatically activated and deactivated with three memory pressure watermarks.
+
+Interface: Module Parameters
+============================
+
+To use this feature, you should first ensure your system is running on a kernel
+that is built with ``CONFIG_DAMON_RECLAIM=y``.
+
+To let sysadmins enable or disable it and tune for the given system,
+DAMON_RECLAIM utilizes module parameters.  That is, you can put
+``damon_reclaim.<parameter>=<value>`` on the kernel boot command line or write
+proper values to ``/sys/module/damon_reclaim/parameters/<parameter>`` files.
+
+Below are the description of each parameter.
+
+enabled
+-------
+
+Enable or disable DAMON_RECLAIM.
+
+You can enable DAMON_RCLAIM by setting the value of this parameter as ``Y``.
+Setting it as ``N`` disables DAMON_RECLAIM.  Note that DAMON_RECLAIM could do
+no real monitoring and reclamation due to the watermarks-based activation
+condition.  Refer to below descriptions for the watermarks parameter for this.
+
+commit_inputs
+-------------
+
+Make DAMON_RECLAIM reads the input parameters again, except ``enabled``.
+
+Input parameters that updated while DAMON_RECLAIM is running are not applied
+by default.  Once this parameter is set as ``Y``, DAMON_RECLAIM reads values
+of parametrs except ``enabled`` again.  Once the re-reading is done, this
+parameter is set as ``N``.  If invalid parameters are found while the
+re-reading, DAMON_RECLAIM will be disabled.
+
+min_age
+-------
+
+Time threshold for cold memory regions identification in microseconds.
+
+If a memory region is not accessed for this or longer time, DAMON_RECLAIM
+identifies the region as cold, and reclaims it.
+
+120 seconds by default.
+
+quota_ms
+--------
+
+Limit of time for the reclamation in milliseconds.
+
+DAMON_RECLAIM tries to use only up to this time within a time window
+(quota_reset_interval_ms) for trying reclamation of cold pages.  This can be
+used for limiting CPU consumption of DAMON_RECLAIM.  If the value is zero, the
+limit is disabled.
+
+10 ms by default.
+
+quota_sz
+--------
+
+Limit of size of memory for the reclamation in bytes.
+
+DAMON_RECLAIM charges amount of memory which it tried to reclaim within a time
+window (quota_reset_interval_ms) and makes no more than this limit is tried.
+This can be used for limiting consumption of CPU and IO.  If this value is
+zero, the limit is disabled.
+
+128 MiB by default.
+
+quota_reset_interval_ms
+-----------------------
+
+The time/size quota charge reset interval in milliseconds.
+
+The charget reset interval for the quota of time (quota_ms) and size
+(quota_sz).  That is, DAMON_RECLAIM does not try reclamation for more than
+quota_ms milliseconds or quota_sz bytes within quota_reset_interval_ms
+milliseconds.
+
+1 second by default.
+
+wmarks_interval
+---------------
+
+Minimal time to wait before checking the watermarks, when DAMON_RECLAIM is
+enabled but inactive due to its watermarks rule.
+
+wmarks_high
+-----------
+
+Free memory rate (per thousand) for the high watermark.
+
+If free memory of the system in bytes per thousand bytes is higher than this,
+DAMON_RECLAIM becomes inactive, so it does nothing but only periodically checks
+the watermarks.
+
+wmarks_mid
+----------
+
+Free memory rate (per thousand) for the middle watermark.
+
+If free memory of the system in bytes per thousand bytes is between this and
+the low watermark, DAMON_RECLAIM becomes active, so starts the monitoring and
+the reclaiming.
+
+wmarks_low
+----------
+
+Free memory rate (per thousand) for the low watermark.
+
+If free memory of the system in bytes per thousand bytes is lower than this,
+DAMON_RECLAIM becomes inactive, so it does nothing but periodically checks the
+watermarks.  In the case, the system falls back to the LRU-list based page
+granularity reclamation logic.
+
+sample_interval
+---------------
+
+Sampling interval for the monitoring in microseconds.
+
+The sampling interval of DAMON for the cold memory monitoring.  Please refer to
+the DAMON documentation (:doc:`usage`) for more detail.
+
+aggr_interval
+-------------
+
+Aggregation interval for the monitoring in microseconds.
+
+The aggregation interval of DAMON for the cold memory monitoring.  Please
+refer to the DAMON documentation (:doc:`usage`) for more detail.
+
+min_nr_regions
+--------------
+
+Minimum number of monitoring regions.
+
+The minimal number of monitoring regions of DAMON for the cold memory
+monitoring.  This can be used to set lower-bound of the monitoring quality.
+But, setting this too high could result in increased monitoring overhead.
+Please refer to the DAMON documentation (:doc:`usage`) for more detail.
+
+max_nr_regions
+--------------
+
+Maximum number of monitoring regions.
+
+The maximum number of monitoring regions of DAMON for the cold memory
+monitoring.  This can be used to set upper-bound of the monitoring overhead.
+However, setting this too low could result in bad monitoring quality.  Please
+refer to the DAMON documentation (:doc:`usage`) for more detail.
+
+monitor_region_start
+--------------------
+
+Start of target memory region in physical address.
+
+The start physical address of memory region that DAMON_RECLAIM will do work
+against.  That is, DAMON_RECLAIM will find cold memory regions in this region
+and reclaims.  By default, biggest System RAM is used as the region.
+
+monitor_region_end
+------------------
+
+End of target memory region in physical address.
+
+The end physical address of memory region that DAMON_RECLAIM will do work
+against.  That is, DAMON_RECLAIM will find cold memory regions in this region
+and reclaims.  By default, biggest System RAM is used as the region.
+
+skip_anon
+---------
+
+Skip anonymous pages reclamation.
+
+If this parameter is set as ``Y``, DAMON_RECLAIM does not reclaim anonymous
+pages.  By default, ``N``.
+
+
+kdamond_pid
+-----------
+
+PID of the DAMON thread.
+
+If DAMON_RECLAIM is enabled, this becomes the PID of the worker thread.  Else,
+-1.
+
+nr_reclaim_tried_regions
+------------------------
+
+Number of memory regions that tried to be reclaimed by DAMON_RECLAIM.
+
+bytes_reclaim_tried_regions
+---------------------------
+
+Total bytes of memory regions that tried to be reclaimed by DAMON_RECLAIM.
+
+nr_reclaimed_regions
+--------------------
+
+Number of memory regions that successfully be reclaimed by DAMON_RECLAIM.
+
+bytes_reclaimed_regions
+-----------------------
+
+Total bytes of memory regions that successfully be reclaimed by DAMON_RECLAIM.
+
+nr_quota_exceeds
+----------------
+
+Number of times that the time/space quota limits have exceeded.
+
+Example
+=======
+
+Below runtime example commands make DAMON_RECLAIM to find memory regions that
+not accessed for 30 seconds or more and pages out.  The reclamation is limited
+to be done only up to 1 GiB per second to avoid DAMON_RECLAIM consuming too
+much CPU time for the paging out operation.  It also asks DAMON_RECLAIM to do
+nothing if the system's free memory rate is more than 50%, but start the real
+works if it becomes lower than 40%.  If DAMON_RECLAIM doesn't make progress and
+therefore the free memory rate becomes lower than 20%, it asks DAMON_RECLAIM to
+do nothing again, so that we can fall back to the LRU-list based page
+granularity reclamation. ::
+
+    # cd /sys/module/damon_reclaim/parameters
+    # echo 30000000 > min_age
+    # echo $((1 * 1024 * 1024 * 1024)) > quota_sz
+    # echo 1000 > quota_reset_interval_ms
+    # echo 500 > wmarks_high
+    # echo 400 > wmarks_mid
+    # echo 200 > wmarks_low
+    # echo Y > enabled
+
+.. [1] https://research.google/pubs/pub48551/
+.. [2] https://lwn.net/Articles/787611/
+.. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html
diff --git a/Documentation/admin-guide/mm/damon/start.rst b/Documentation/admin-guide/mm/damon/start.rst
new file mode 100644
index 0000000000..7aa0071ff1
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/start.rst
@@ -0,0 +1,127 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Getting Started
+===============
+
+This document briefly describes how you can use DAMON by demonstrating its
+default user space tool.  Please note that this document describes only a part
+of its features for brevity.  Please refer to the usage `doc
+<https://github.com/awslabs/damo/blob/next/USAGE.md>`_ of the tool for more
+details.
+
+
+Prerequisites
+=============
+
+Kernel
+------
+
+You should first ensure your system is running on a kernel built with
+``CONFIG_DAMON_*=y``.
+
+
+User Space Tool
+---------------
+
+For the demonstration, we will use the default user space tool for DAMON,
+called DAMON Operator (DAMO).  It is available at
+https://github.com/awslabs/damo.  The examples below assume that ``damo`` is on
+your ``$PATH``.  It's not mandatory, though.
+
+Because DAMO is using the sysfs interface (refer to :doc:`usage` for the
+detail) of DAMON, you should ensure :doc:`sysfs </filesystems/sysfs>` is
+mounted.
+
+
+Recording Data Access Patterns
+==============================
+
+The commands below record the memory access patterns of a program and save the
+monitoring results to 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 download an artificial memory access
+generator program and run it in the background.  The generator 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 the ``damon.data`` file.
+
+
+Visualizing Recorded Patterns
+=============================
+
+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
+===========================================
+
+Below command makes every memory region of size >=4K that has not accessed for
+>=60 seconds in your workload to be swapped out. ::
+
+    $ sudo damo schemes --damos_access_rate 0 0 --damos_sz_region 4K max \
+                        --damos_age 60s max --damos_action pageout \
+                        <pid of your workload>
diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
new file mode 100644
index 0000000000..8da1b72818
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -0,0 +1,812 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Detailed Usages
+===============
+
+DAMON provides below interfaces for different users.
+
+- *DAMON user space tool.*
+  `This <https://github.com/awslabs/damo>`_ is for privileged people such as
+  system administrators who want a just-working human-friendly interface.
+  Using this, users can use the DAMON’s major features in a human-friendly way.
+  It may not be highly tuned for special cases, though.  For more detail,
+  please refer to its `usage document
+  <https://github.com/awslabs/damo/blob/next/USAGE.md>`_.
+- *sysfs interface.*
+  :ref:`This <sysfs_interface>` is for privileged user space programmers who
+  want more optimized use of DAMON.  Using this, users can use DAMON’s major
+  features by reading from and writing to special sysfs files.  Therefore,
+  you can write and use your personalized DAMON sysfs wrapper programs that
+  reads/writes the sysfs files instead of you.  The `DAMON user space tool
+  <https://github.com/awslabs/damo>`_ is one example of such programs.
+- *debugfs interface. (DEPRECATED!)*
+  :ref:`This <debugfs_interface>` is almost identical to :ref:`sysfs interface
+  <sysfs_interface>`.  This is deprecated, so users should move to the
+  :ref:`sysfs interface <sysfs_interface>`.  If you depend on this and cannot
+  move, please report your usecase to damon@lists.linux.dev and
+  linux-mm@kvack.org.
+- *Kernel Space Programming Interface.*
+  :doc:`This </mm/damon/api>` is for kernel space programmers.  Using this,
+  users can utilize every feature of DAMON most flexibly and efficiently by
+  writing kernel space DAMON application programs for you.  You can even extend
+  DAMON for various address spaces.  For detail, please refer to the interface
+  :doc:`document </mm/damon/api>`.
+
+.. _sysfs_interface:
+
+sysfs Interface
+===============
+
+DAMON sysfs interface is built when ``CONFIG_DAMON_SYSFS`` is defined.  It
+creates multiple directories and files under its sysfs directory,
+``<sysfs>/kernel/mm/damon/``.  You can control DAMON by writing to and reading
+from the files under the directory.
+
+For a short example, users can monitor the virtual address space of a given
+workload as below. ::
+
+    # cd /sys/kernel/mm/damon/admin/
+    # echo 1 > kdamonds/nr_kdamonds && echo 1 > kdamonds/0/contexts/nr_contexts
+    # echo vaddr > kdamonds/0/contexts/0/operations
+    # echo 1 > kdamonds/0/contexts/0/targets/nr_targets
+    # echo $(pidof <workload>) > kdamonds/0/contexts/0/targets/0/pid_target
+    # echo on > kdamonds/0/state
+
+Files Hierarchy
+---------------
+
+The files hierarchy of DAMON sysfs interface is shown below.  In the below
+figure, parents-children relations are represented with indentations, each
+directory is having ``/`` suffix, and files in each directory are separated by
+comma (","). ::
+
+    /sys/kernel/mm/damon/admin
+    │ kdamonds/nr_kdamonds
+    │ │ 0/state,pid
+    │ │ │ contexts/nr_contexts
+    │ │ │ │ 0/avail_operations,operations
+    │ │ │ │ │ monitoring_attrs/
+    │ │ │ │ │ │ intervals/sample_us,aggr_us,update_us
+    │ │ │ │ │ │ nr_regions/min,max
+    │ │ │ │ │ targets/nr_targets
+    │ │ │ │ │ │ 0/pid_target
+    │ │ │ │ │ │ │ regions/nr_regions
+    │ │ │ │ │ │ │ │ 0/start,end
+    │ │ │ │ │ │ │ │ ...
+    │ │ │ │ │ │ ...
+    │ │ │ │ │ schemes/nr_schemes
+    │ │ │ │ │ │ 0/action
+    │ │ │ │ │ │ │ access_pattern/
+    │ │ │ │ │ │ │ │ sz/min,max
+    │ │ │ │ │ │ │ │ nr_accesses/min,max
+    │ │ │ │ │ │ │ │ age/min,max
+    │ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms
+    │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
+    │ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low
+    │ │ │ │ │ │ │ filters/nr_filters
+    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
+    │ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds
+    │ │ │ │ │ │ │ tried_regions/total_bytes
+    │ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age
+    │ │ │ │ │ │ │ │ ...
+    │ │ │ │ │ │ ...
+    │ │ │ │ ...
+    │ │ ...
+
+Root
+----
+
+The root of the DAMON sysfs interface is ``<sysfs>/kernel/mm/damon/``, and it
+has one directory named ``admin``.  The directory contains the files for
+privileged user space programs' control of DAMON.  User space tools or daemons
+having the root permission could use this directory.
+
+kdamonds/
+---------
+
+The monitoring-related information including request specifications and results
+are called DAMON context.  DAMON executes each context with a kernel thread
+called kdamond, and multiple kdamonds could run in parallel.
+
+Under the ``admin`` directory, one directory, ``kdamonds``, which has files for
+controlling the kdamonds exist.  In the beginning, this directory has only one
+file, ``nr_kdamonds``.  Writing a number (``N``) to the file creates the number
+of child directories named ``0`` to ``N-1``.  Each directory represents each
+kdamond.
+
+kdamonds/<N>/
+-------------
+
+In each kdamond directory, two files (``state`` and ``pid``) and one directory
+(``contexts``) exist.
+
+Reading ``state`` returns ``on`` if the kdamond is currently running, or
+``off`` if it is not running.  Writing ``on`` or ``off`` makes the kdamond be
+in the state.  Writing ``commit`` to the ``state`` file makes kdamond reads the
+user inputs in the sysfs files except ``state`` file again.  Writing
+``update_schemes_stats`` to ``state`` file updates the contents of stats files
+for each DAMON-based operation scheme of the kdamond.  For details of the
+stats, please refer to :ref:`stats section <sysfs_schemes_stats>`.
+
+Writing ``update_schemes_tried_regions`` to ``state`` file updates the
+DAMON-based operation scheme action tried regions directory for each
+DAMON-based operation scheme of the kdamond.  Writing
+``update_schemes_tried_bytes`` to ``state`` file updates only
+``.../tried_regions/total_bytes`` files.  Writing
+``clear_schemes_tried_regions`` to ``state`` file clears the DAMON-based
+operating scheme action tried regions directory for each DAMON-based operation
+scheme of the kdamond.  For details of the DAMON-based operation scheme action
+tried regions directory, please refer to :ref:`tried_regions section
+<sysfs_schemes_tried_regions>`.
+
+If the state is ``on``, reading ``pid`` shows the pid of the kdamond thread.
+
+``contexts`` directory contains files for controlling the monitoring contexts
+that this kdamond will execute.
+
+kdamonds/<N>/contexts/
+----------------------
+
+In the beginning, this directory has only one file, ``nr_contexts``.  Writing a
+number (``N``) to the file creates the number of child directories named as
+``0`` to ``N-1``.  Each directory represents each monitoring context.  At the
+moment, only one context per kdamond is supported, so only ``0`` or ``1`` can
+be written to the file.
+
+.. _sysfs_contexts:
+
+contexts/<N>/
+-------------
+
+In each context directory, two files (``avail_operations`` and ``operations``)
+and three directories (``monitoring_attrs``, ``targets``, and ``schemes``)
+exist.
+
+DAMON supports multiple types of monitoring operations, including those for
+virtual address space and the physical address space.  You can get the list of
+available monitoring operations set on the currently running kernel by reading
+``avail_operations`` file.  Based on the kernel configuration, the file will
+list some or all of below keywords.
+
+ - vaddr: Monitor virtual address spaces of specific processes
+ - fvaddr: Monitor fixed virtual address ranges
+ - paddr: Monitor the physical address space of the system
+
+Please refer to :ref:`regions sysfs directory <sysfs_regions>` for detailed
+differences between the operations sets in terms of the monitoring target
+regions.
+
+You can set and get what type of monitoring operations DAMON will use for the
+context by writing one of the keywords listed in ``avail_operations`` file and
+reading from the ``operations`` file.
+
+.. _sysfs_monitoring_attrs:
+
+contexts/<N>/monitoring_attrs/
+------------------------------
+
+Files for specifying attributes of the monitoring including required quality
+and efficiency of the monitoring are in ``monitoring_attrs`` directory.
+Specifically, two directories, ``intervals`` and ``nr_regions`` exist in this
+directory.
+
+Under ``intervals`` directory, three files for DAMON's sampling interval
+(``sample_us``), aggregation interval (``aggr_us``), and update interval
+(``update_us``) exist.  You can set and get the values in micro-seconds by
+writing to and reading from the files.
+
+Under ``nr_regions`` directory, two files for the lower-bound and upper-bound
+of DAMON's monitoring regions (``min`` and ``max``, respectively), which
+controls the monitoring overhead, exist.  You can set and get the values by
+writing to and rading from the files.
+
+For more details about the intervals and monitoring regions range, please refer
+to the Design document (:doc:`/mm/damon/design`).
+
+contexts/<N>/targets/
+---------------------
+
+In the beginning, this directory has only one file, ``nr_targets``.  Writing a
+number (``N``) to the file creates the number of child directories named ``0``
+to ``N-1``.  Each directory represents each monitoring target.
+
+targets/<N>/
+------------
+
+In each target directory, one file (``pid_target``) and one directory
+(``regions``) exist.
+
+If you wrote ``vaddr`` to the ``contexts/<N>/operations``, each target should
+be a process.  You can specify the process to DAMON by writing the pid of the
+process to the ``pid_target`` file.
+
+.. _sysfs_regions:
+
+targets/<N>/regions
+-------------------
+
+When ``vaddr`` monitoring operations set is being used (``vaddr`` is written to
+the ``contexts/<N>/operations`` file), DAMON automatically sets and updates the
+monitoring target regions so that entire memory mappings of target processes
+can be covered.  However, users could want to set the initial monitoring region
+to specific address ranges.
+
+In contrast, DAMON do not automatically sets and updates the monitoring target
+regions when ``fvaddr`` or ``paddr`` monitoring operations sets are being used
+(``fvaddr`` or ``paddr`` have written to the ``contexts/<N>/operations``).
+Therefore, users should set the monitoring target regions by themselves in the
+cases.
+
+For such cases, users can explicitly set the initial monitoring target regions
+as they want, by writing proper values to the files under this directory.
+
+In the beginning, this directory has only one file, ``nr_regions``.  Writing a
+number (``N``) to the file creates the number of child directories named ``0``
+to ``N-1``.  Each directory represents each initial monitoring target region.
+
+regions/<N>/
+------------
+
+In each region directory, you will find two files (``start`` and ``end``).  You
+can set and get the start and end addresses of the initial monitoring target
+region by writing to and reading from the files, respectively.
+
+Each region should not overlap with others.  ``end`` of directory ``N`` should
+be equal or smaller than ``start`` of directory ``N+1``.
+
+contexts/<N>/schemes/
+---------------------
+
+The directory for DAMON-based Operation Schemes (:ref:`DAMOS
+<damon_design_damos>`).  Users can get and set the schemes by reading from and
+writing to files under this directory.
+
+In the beginning, this directory has only one file, ``nr_schemes``.  Writing a
+number (``N``) to the file creates the number of child directories named ``0``
+to ``N-1``.  Each directory represents each DAMON-based operation scheme.
+
+schemes/<N>/
+------------
+
+In each scheme directory, five directories (``access_pattern``, ``quotas``,
+``watermarks``, ``filters``, ``stats``, and ``tried_regions``) and one file
+(``action``) exist.
+
+The ``action`` file is for setting and getting the scheme's :ref:`action
+<damon_design_damos_action>`.  The keywords that can be written to and read
+from the file and their meaning are as below.
+
+Note that support of each action depends on the running DAMON operations set
+:ref:`implementation <sysfs_contexts>`.
+
+ - ``willneed``: Call ``madvise()`` for the region with ``MADV_WILLNEED``.
+   Supported by ``vaddr`` and ``fvaddr`` operations set.
+ - ``cold``: Call ``madvise()`` for the region with ``MADV_COLD``.
+   Supported by ``vaddr`` and ``fvaddr`` operations set.
+ - ``pageout``: Call ``madvise()`` for the region with ``MADV_PAGEOUT``.
+   Supported by ``vaddr``, ``fvaddr`` and ``paddr`` operations set.
+ - ``hugepage``: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``.
+   Supported by ``vaddr`` and ``fvaddr`` operations set.
+ - ``nohugepage``: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``.
+   Supported by ``vaddr`` and ``fvaddr`` operations set.
+ - ``lru_prio``: Prioritize the region on its LRU lists.
+   Supported by ``paddr`` operations set.
+ - ``lru_deprio``: Deprioritize the region on its LRU lists.
+   Supported by ``paddr`` operations set.
+ - ``stat``: Do nothing but count the statistics.
+   Supported by all operations sets.
+
+schemes/<N>/access_pattern/
+---------------------------
+
+The directory for the target access :ref:`pattern
+<damon_design_damos_access_pattern>` of the given DAMON-based operation scheme.
+
+Under the ``access_pattern`` directory, three directories (``sz``,
+``nr_accesses``, and ``age``) each having two files (``min`` and ``max``)
+exist.  You can set and get the access pattern for the given scheme by writing
+to and reading from the ``min`` and ``max`` files under ``sz``,
+``nr_accesses``, and ``age`` directories, respectively.  Note that the ``min``
+and the ``max`` form a closed interval.
+
+schemes/<N>/quotas/
+-------------------
+
+The directory for the :ref:`quotas <damon_design_damos_quotas>` of the given
+DAMON-based operation scheme.
+
+Under ``quotas`` directory, three files (``ms``, ``bytes``,
+``reset_interval_ms``) and one directory (``weights``) having three files
+(``sz_permil``, ``nr_accesses_permil``, and ``age_permil``) in it exist.
+
+You can set the ``time quota`` in milliseconds, ``size quota`` in bytes, and
+``reset interval`` in milliseconds by writing the values to the three files,
+respectively.  Then, DAMON tries to use only up to ``time quota`` milliseconds
+for applying the ``action`` to memory regions of the ``access_pattern``, and to
+apply the action to only up to ``bytes`` bytes of memory regions within the
+``reset_interval_ms``.  Setting both ``ms`` and ``bytes`` zero disables the
+quota limits.
+
+You can also set the :ref:`prioritization weights
+<damon_design_damos_quotas_prioritization>` for size, access frequency, and age
+in per-thousand unit by writing the values to the three files under the
+``weights`` directory.
+
+schemes/<N>/watermarks/
+-----------------------
+
+The directory for the :ref:`watermarks <damon_design_damos_watermarks>` of the
+given DAMON-based operation scheme.
+
+Under the watermarks directory, five files (``metric``, ``interval_us``,
+``high``, ``mid``, and ``low``) for setting the metric, the time interval
+between check of the metric, and the three watermarks exist.  You can set and
+get the five values by writing to the files, respectively.
+
+Keywords and meanings of those that can be written to the ``metric`` file are
+as below.
+
+ - none: Ignore the watermarks
+ - free_mem_rate: System's free memory rate (per thousand)
+
+The ``interval`` should written in microseconds unit.
+
+schemes/<N>/filters/
+--------------------
+
+The directory for the :ref:`filters <damon_design_damos_filters>` of the given
+DAMON-based operation scheme.
+
+In the beginning, this directory has only one file, ``nr_filters``.  Writing a
+number (``N``) to the file creates the number of child directories named ``0``
+to ``N-1``.  Each directory represents each filter.  The filters are evaluated
+in the numeric order.
+
+Each filter directory contains six files, namely ``type``, ``matcing``,
+``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``.  To ``type``
+file, you can write one of four special keywords: ``anon`` for anonymous pages,
+``memcg`` for specific memory cgroup, ``addr`` for specific address range (an
+open-ended interval), or ``target`` for specific DAMON monitoring target
+filtering.  In case of the memory cgroup filtering, you can specify the memory
+cgroup of the interest by writing the path of the memory cgroup from the
+cgroups mount point to ``memcg_path`` file.  In case of the address range
+filtering, you can specify the start and end address of the range to
+``addr_start`` and ``addr_end`` files, respectively.  For the DAMON monitoring
+target filtering, you can specify the index of the target between the list of
+the DAMON context's monitoring targets list to ``target_idx`` file.  You can
+write ``Y`` or ``N`` to ``matching`` file to filter out pages that does or does
+not match to the type, respectively.  Then, the scheme's action will not be
+applied to the pages that specified to be filtered out.
+
+For example, below restricts a DAMOS action to be applied to only non-anonymous
+pages of all memory cgroups except ``/having_care_already``.::
+
+    # echo 2 > nr_filters
+    # # filter out anonymous pages
+    echo anon > 0/type
+    echo Y > 0/matching
+    # # further filter out all cgroups except one at '/having_care_already'
+    echo memcg > 1/type
+    echo /having_care_already > 1/memcg_path
+    echo N > 1/matching
+
+Note that ``anon`` and ``memcg`` filters are currently supported only when
+``paddr`` `implementation <sysfs_contexts>` is being used.
+
+Also, memory regions that are filtered out by ``addr`` or ``target`` filters
+are not counted as the scheme has tried to those, while regions that filtered
+out by other type filters are counted as the scheme has tried to.  The
+difference is applied to :ref:`stats <damos_stats>` and
+:ref:`tried regions <sysfs_schemes_tried_regions>`.
+
+.. _sysfs_schemes_stats:
+
+schemes/<N>/stats/
+------------------
+
+DAMON counts the total number and bytes of regions that each scheme is tried to
+be applied, the two numbers for the regions that each scheme is successfully
+applied, and the total number of the quota limit exceeds.  This statistics can
+be used for online analysis or tuning of the schemes.
+
+The statistics can be retrieved by reading the files under ``stats`` directory
+(``nr_tried``, ``sz_tried``, ``nr_applied``, ``sz_applied``, and
+``qt_exceeds``), respectively.  The files are not updated in real time, so you
+should ask DAMON sysfs interface to update the content of the files for the
+stats by writing a special keyword, ``update_schemes_stats`` to the relevant
+``kdamonds/<N>/state`` file.
+
+.. _sysfs_schemes_tried_regions:
+
+schemes/<N>/tried_regions/
+--------------------------
+
+This directory initially has one file, ``total_bytes``.
+
+When a special keyword, ``update_schemes_tried_regions``, is written to the
+relevant ``kdamonds/<N>/state`` file, DAMON updates the ``total_bytes`` file so
+that reading it returns the total size of the scheme tried regions, and creates
+directories named integer starting from ``0`` under this directory.  Each
+directory contains files exposing detailed information about each of the memory
+region that the corresponding scheme's ``action`` has tried to be applied under
+this directory, during next :ref:`aggregation interval
+<sysfs_monitoring_attrs>`.  The information includes address range,
+``nr_accesses``, and ``age`` of the region.
+
+Writing ``update_schemes_tried_bytes`` to the relevant ``kdamonds/<N>/state``
+file will only update the ``total_bytes`` file, and will not create the
+subdirectories.
+
+The directories will be removed when another special keyword,
+``clear_schemes_tried_regions``, is written to the relevant
+``kdamonds/<N>/state`` file.
+
+The expected usage of this directory is investigations of schemes' behaviors,
+and query-like efficient data access monitoring results retrievals.  For the
+latter use case, in particular, users can set the ``action`` as ``stat`` and
+set the ``access pattern`` as their interested pattern that they want to query.
+
+tried_regions/<N>/
+------------------
+
+In each region directory, you will find four files (``start``, ``end``,
+``nr_accesses``, and ``age``).  Reading the files will show the start and end
+addresses, ``nr_accesses``, and ``age`` of the region that corresponding
+DAMON-based operation scheme ``action`` has tried to be applied.
+
+Example
+~~~~~~~
+
+Below commands applies a scheme saying "If a memory region of size in [4KiB,
+8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate
+interval in [10, 20], page out the region.  For the paging out, use only up to
+10ms per second, and also don't page out more than 1GiB per second.  Under the
+limitation, page out memory regions having longer age first.  Also, check the
+free memory rate of the system every 5 seconds, start the monitoring and paging
+out when the free memory rate becomes lower than 50%, but stop it if the free
+memory rate becomes larger than 60%, or lower than 30%". ::
+
+    # cd <sysfs>/kernel/mm/damon/admin
+    # # populate directories
+    # echo 1 > kdamonds/nr_kdamonds; echo 1 > kdamonds/0/contexts/nr_contexts;
+    # echo 1 > kdamonds/0/contexts/0/schemes/nr_schemes
+    # cd kdamonds/0/contexts/0/schemes/0
+    # # set the basic access pattern and the action
+    # echo 4096 > access_pattern/sz/min
+    # echo 8192 > access_pattern/sz/max
+    # echo 0 > access_pattern/nr_accesses/min
+    # echo 5 > access_pattern/nr_accesses/max
+    # echo 10 > access_pattern/age/min
+    # echo 20 > access_pattern/age/max
+    # echo pageout > action
+    # # set quotas
+    # echo 10 > quotas/ms
+    # echo $((1024*1024*1024)) > quotas/bytes
+    # echo 1000 > quotas/reset_interval_ms
+    # # set watermark
+    # echo free_mem_rate > watermarks/metric
+    # echo 5000000 > watermarks/interval_us
+    # echo 600 > watermarks/high
+    # echo 500 > watermarks/mid
+    # echo 300 > watermarks/low
+
+Please note that it's highly recommended to use user space tools like `damo
+<https://github.com/awslabs/damo>`_ rather than manually reading and writing
+the files as above.  Above is only for an example.
+
+.. _debugfs_interface:
+
+debugfs Interface (DEPRECATED!)
+===============================
+
+.. note::
+
+  THIS IS DEPRECATED!
+
+  DAMON debugfs interface is deprecated, so users should move to the
+  :ref:`sysfs interface <sysfs_interface>`.  If you depend on this and cannot
+  move, please report your usecase to damon@lists.linux.dev and
+  linux-mm@kvack.org.
+
+DAMON exports eight files, ``attrs``, ``target_ids``, ``init_regions``,
+``schemes``, ``monitor_on``, ``kdamond_pid``, ``mk_contexts`` and
+``rm_contexts`` under its debugfs directory, ``<debugfs>/damon/``.
+
+
+Attributes
+----------
+
+Users can get and set the ``sampling interval``, ``aggregation interval``,
+``update interval``, and min/max number of monitoring target regions by
+reading from and writing to the ``attrs`` file.  To know about the monitoring
+attributes in detail, please refer to the :doc:`/mm/damon/design`.  For
+example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10 and
+1000, and then check it again::
+
+    # cd <debugfs>/damon
+    # echo 5000 100000 1000000 10 1000 > attrs
+    # cat attrs
+    5000 100000 1000000 10 1000
+
+
+Target IDs
+----------
+
+Some types of address spaces supports multiple monitoring target.  For example,
+the virtual memory address spaces monitoring can have multiple processes as the
+monitoring targets.  Users can set the targets by writing relevant id values of
+the targets to, and get the ids of the current targets by reading from the
+``target_ids`` file.  In case of the virtual address spaces monitoring, the
+values should be pids of the monitoring target processes.  For example, below
+commands set processes having pids 42 and 4242 as the monitoring targets and
+check it again::
+
+    # cd <debugfs>/damon
+    # echo 42 4242 > target_ids
+    # cat target_ids
+    42 4242
+
+Users can also monitor the physical memory address space of the system by
+writing a special keyword, "``paddr\n``" to the file.  Because physical address
+space monitoring doesn't support multiple targets, reading the file will show a
+fake value, ``42``, as below::
+
+    # cd <debugfs>/damon
+    # echo paddr > target_ids
+    # cat target_ids
+    42
+
+Note that setting the target ids doesn't start the monitoring.
+
+
+Initial Monitoring Target Regions
+---------------------------------
+
+In case of the virtual address space monitoring, DAMON automatically sets and
+updates the monitoring target regions so that entire memory mappings of target
+processes can be covered.  However, users can want to limit the monitoring
+region to specific address ranges, such as the heap, the stack, or specific
+file-mapped area.  Or, some users can know the initial access pattern of their
+workloads and therefore want to set optimal initial regions for the 'adaptive
+regions adjustment'.
+
+In contrast, DAMON do not automatically sets and updates the monitoring target
+regions in case of physical memory monitoring.  Therefore, users should set the
+monitoring target regions by themselves.
+
+In such cases, users can explicitly set the initial monitoring target regions
+as they want, by writing proper values to the ``init_regions`` file.  The input
+should be a sequence of three integers separated by white spaces that represent
+one region in below form.::
+
+    <target idx> <start address> <end address>
+
+The ``target idx`` should be the index of the target in ``target_ids`` file,
+starting from ``0``, and the regions should be passed in address order.  For
+example, below commands will set a couple of address ranges, ``1-100`` and
+``100-200`` as the initial monitoring target region of pid 42, which is the
+first one (index ``0``) in ``target_ids``, and another couple of address
+ranges, ``20-40`` and ``50-100`` as that of pid 4242, which is the second one
+(index ``1``) in ``target_ids``.::
+
+    # cd <debugfs>/damon
+    # cat target_ids
+    42 4242
+    # echo "0   1       100 \
+            0   100     200 \
+            1   20      40  \
+            1   50      100" > init_regions
+
+Note that this sets the initial monitoring target regions only.  In case of
+virtual memory monitoring, DAMON will automatically updates the boundary of the
+regions after one ``update interval``.  Therefore, users should set the
+``update interval`` large enough in this case, if they don't want the
+update.
+
+
+Schemes
+-------
+
+Users can get and set the DAMON-based operation :ref:`schemes
+<damon_design_damos>` by reading from and writing to ``schemes`` debugfs file.
+Reading the file also shows the statistics of each scheme.  To the file, each
+of the schemes should be represented in each line in below form::
+
+    <target access pattern> <action> <quota> <watermarks>
+
+You can disable schemes by simply writing an empty string to the file.
+
+Target Access Pattern
+~~~~~~~~~~~~~~~~~~~~~
+
+The target access :ref:`pattern <damon_design_damos_access_pattern>` of the
+scheme.  The ``<target access pattern>`` is constructed with three ranges in
+below form::
+
+    min-size max-size min-acc max-acc min-age max-age
+
+Specifically, bytes for the size of regions (``min-size`` and ``max-size``),
+number of monitored accesses per aggregate interval for access frequency
+(``min-acc`` and ``max-acc``), number of aggregate intervals for the age of
+regions (``min-age`` and ``max-age``) are specified.  Note that the ranges are
+closed interval.
+
+Action
+~~~~~~
+
+The ``<action>`` is a predefined integer for memory management :ref:`actions
+<damon_design_damos_action>`.  The supported numbers and their meanings are as
+below.
+
+ - 0: Call ``madvise()`` for the region with ``MADV_WILLNEED``.  Ignored if
+   ``target`` is ``paddr``.
+ - 1: Call ``madvise()`` for the region with ``MADV_COLD``.  Ignored if
+   ``target`` is ``paddr``.
+ - 2: Call ``madvise()`` for the region with ``MADV_PAGEOUT``.
+ - 3: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``.  Ignored if
+   ``target`` is ``paddr``.
+ - 4: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``.  Ignored if
+   ``target`` is ``paddr``.
+ - 5: Do nothing but count the statistics
+
+Quota
+~~~~~
+
+Users can set the :ref:`quotas <damon_design_damos_quotas>` of the given scheme
+via the ``<quota>`` in below form::
+
+    <ms> <sz> <reset interval> <priority weights>
+
+This makes DAMON to try to use only up to ``<ms>`` milliseconds for applying
+the action to memory regions of the ``target access pattern`` within the
+``<reset interval>`` milliseconds, and to apply the action to only up to
+``<sz>`` bytes of memory regions within the ``<reset interval>``.  Setting both
+``<ms>`` and ``<sz>`` zero disables the quota limits.
+
+For the :ref:`prioritization <damon_design_damos_quotas_prioritization>`, users
+can set the weights for the three properties in ``<priority weights>`` in below
+form::
+
+    <size weight> <access frequency weight> <age weight>
+
+Watermarks
+~~~~~~~~~~
+
+Users can specify :ref:`watermarks <damon_design_damos_watermarks>` of the
+given scheme via ``<watermarks>`` in below form::
+
+    <metric> <check interval> <high mark> <middle mark> <low mark>
+
+``<metric>`` is a predefined integer for the metric to be checked.  The
+supported numbers and their meanings are as below.
+
+ - 0: Ignore the watermarks
+ - 1: System's free memory rate (per thousand)
+
+The value of the metric is checked every ``<check interval>`` microseconds.
+
+If the value is higher than ``<high mark>`` or lower than ``<low mark>``, the
+scheme is deactivated.  If the value is lower than ``<mid mark>``, the scheme
+is activated.
+
+.. _damos_stats:
+
+Statistics
+~~~~~~~~~~
+
+It also counts the total number and bytes of regions that each scheme is tried
+to be applied, the two numbers for the regions that each scheme is successfully
+applied, and the total number of the quota limit exceeds.  This statistics can
+be used for online analysis or tuning of the schemes.
+
+The statistics can be shown by reading the ``schemes`` file.  Reading the file
+will show each scheme you entered in each line, and the five numbers for the
+statistics will be added at the end of each line.
+
+Example
+~~~~~~~
+
+Below commands applies a scheme saying "If a memory region of size in [4KiB,
+8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate
+interval in [10, 20], page out the region.  For the paging out, use only up to
+10ms per second, and also don't page out more than 1GiB per second.  Under the
+limitation, page out memory regions having longer age first.  Also, check the
+free memory rate of the system every 5 seconds, start the monitoring and paging
+out when the free memory rate becomes lower than 50%, but stop it if the free
+memory rate becomes larger than 60%, or lower than 30%".::
+
+    # cd <debugfs>/damon
+    # scheme="4096 8192  0 5    10 20    2"  # target access pattern and action
+    # scheme+=" 10 $((1024*1024*1024)) 1000" # quotas
+    # scheme+=" 0 0 100"                     # prioritization weights
+    # scheme+=" 1 5000000 600 500 300"       # watermarks
+    # echo "$scheme" > schemes
+
+
+Turning On/Off
+--------------
+
+Setting the files as described above doesn't incur effect unless you explicitly
+start the monitoring.  You can start, stop, and check the current status of the
+monitoring by writing to and reading from the ``monitor_on`` file.  Writing
+``on`` to the file starts the monitoring of the targets with the attributes.
+Writing ``off`` to the file stops those.  DAMON also stops if every target
+process is terminated.  Below example commands turn on, off, and check the
+status of DAMON::
+
+    # cd <debugfs>/damon
+    # echo on > monitor_on
+    # echo off > monitor_on
+    # cat monitor_on
+    off
+
+Please note that you cannot write to the above-mentioned debugfs files while
+the monitoring is turned on.  If you write to the files while DAMON is running,
+an error code such as ``-EBUSY`` will be returned.
+
+
+Monitoring Thread PID
+---------------------
+
+DAMON does requested monitoring with a kernel thread called ``kdamond``.  You
+can get the pid of the thread by reading the ``kdamond_pid`` file.  When the
+monitoring is turned off, reading the file returns ``none``. ::
+
+    # cd <debugfs>/damon
+    # cat monitor_on
+    off
+    # cat kdamond_pid
+    none
+    # echo on > monitor_on
+    # cat kdamond_pid
+    18594
+
+
+Using Multiple Monitoring Threads
+---------------------------------
+
+One ``kdamond`` thread is created for each monitoring context.  You can create
+and remove monitoring contexts for multiple ``kdamond`` required use case using
+the ``mk_contexts`` and ``rm_contexts`` files.
+
+Writing the name of the new context to the ``mk_contexts`` file creates a
+directory of the name on the DAMON debugfs directory.  The directory will have
+DAMON debugfs files for the context. ::
+
+    # cd <debugfs>/damon
+    # ls foo
+    # ls: cannot access 'foo': No such file or directory
+    # echo foo > mk_contexts
+    # ls foo
+    # attrs  init_regions  kdamond_pid  schemes  target_ids
+
+If the context is not needed anymore, you can remove it and the corresponding
+directory by putting the name of the context to the ``rm_contexts`` file. ::
+
+    # echo foo > rm_contexts
+    # ls foo
+    # ls: cannot access 'foo': No such file or directory
+
+Note that ``mk_contexts``, ``rm_contexts``, and ``monitor_on`` files are in the
+root directory only.
+
+
+.. _tracepoint:
+
+Tracepoint for Monitoring Results
+=================================
+
+Users can get the monitoring results via the :ref:`tried_regions
+<sysfs_schemes_tried_regions>` or a tracepoint, ``damon:damon_aggregated``.
+While the tried regions directory is useful for getting a snapshot, the
+tracepoint is useful for getting a full record of the results.  While the
+monitoring is turned on, you could record the tracepoint events and show
+results using tracepoint supporting tools like ``perf``.  For example::
+
+    # echo on > monitor_on
+    # perf record -e damon:damon_aggregated &
+    # sleep 5
+    # kill 9 $(pidof perf)
+    # echo off > monitor_on
+    # perf script