[PATCH 00/10] Docs/mm/damon: Minor fixes and design doc update

[PATCH 00/10] Docs/mm/damon: Minor fixes and design doc update

[SeongJae Park]

Some of DAMON documents are outdated, or having minor typos or grammar
erros.  Especially, the design doc has not updated for DAMOS, which is
an important part of DAMON.  Fix the minor issues and update documents.

SeongJae Park (10):
  Docs/mm/damon/faq: remove old questions
  Docs/mm/damon/maintainer-profile: fix typos and grammar errors
  Docs/mm/damon/design: add a section for overall architecture
  Docs/mm/damon/design: update the layout based on the layers
  Docs/mm/damon/design: rewrite configurable layers
  Docs/mm/damon/design: add a section for the relation between Core and
    Modules layer
  Docs/mm/damon/design: add sections for basic parts of DAMOS
  Docs/mm/damon/design: add sections for advanced features of DAMOS
  Docs/mm/damon/design: add a section for DAMON core API
  Docs/mm/damon/design: add a section for the modules layer

 Documentation/mm/damon/design.rst             | 309 ++++++++++++++++--
 Documentation/mm/damon/faq.rst                |  23 --
 Documentation/mm/damon/maintainer-profile.rst |   4 +-
 3 files changed, 285 insertions(+), 51 deletions(-)

-- 
2.25.1

[PATCH 01/10] Docs/mm/damon/faq: remove old questions

[SeongJae Park]

The first two questions of DAMON faqs have raised when DAMON patches
were first submitted.  More than one year has passed since DAMON patches
get merged in the mainline, and that kind of questions are not asked
nowadays.  Remove the questions.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/faq.rst | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/Documentation/mm/damon/faq.rst b/Documentation/mm/damon/faq.rst
index dde7e2414ee6..3279dc7a8211 100644
--- a/Documentation/mm/damon/faq.rst
+++ b/Documentation/mm/damon/faq.rst
@@ -4,29 +4,6 @@
 Frequently Asked Questions
 ==========================
 
-Why a new subsystem, instead of extending perf or other user space tools?
-=========================================================================
-
-First, because it needs to be lightweight as much as possible so that it can be
-used online, any unnecessary overhead such as kernel - user space context
-switching cost should be avoided.  Second, DAMON aims to be used by other
-programs including the kernel.  Therefore, having a dependency on specific
-tools like perf is not desirable.  These are the two biggest reasons why DAMON
-is implemented in the kernel space.
-
-
-Can 'idle pages tracking' or 'perf mem' substitute DAMON?
-=========================================================
-
-Idle page tracking is a low level primitive for access check of the physical
-address space.  'perf mem' is similar, though it can use sampling to minimize
-the overhead.  On the other hand, DAMON is a higher-level framework for the
-monitoring of various address spaces.  It is focused on memory management
-optimization and provides sophisticated accuracy/overhead handling mechanisms.
-Therefore, 'idle pages tracking' and 'perf mem' could provide a subset of
-DAMON's output, but cannot substitute DAMON.
-
-
 Does DAMON support virtual memory only?
 =======================================
 
-- 
2.25.1

[PATCH 02/10] Docs/mm/damon/maintainer-profile: fix typos and grammar errors

[SeongJae Park]

Fix a few typos and grammar erros in DAMON Maintainer Profile document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/maintainer-profile.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/mm/damon/maintainer-profile.rst b/Documentation/mm/damon/maintainer-profile.rst
index 24a202f03de8..a84c14e59053 100644
--- a/Documentation/mm/damon/maintainer-profile.rst
+++ b/Documentation/mm/damon/maintainer-profile.rst
@@ -3,7 +3,7 @@
 DAMON Maintainer Entry Profile
 ==============================
 
-The DAMON subsystem covers the files that listed in 'DATA ACCESS MONITOR'
+The DAMON subsystem covers the files that are listed in 'DATA ACCESS MONITOR'
 section of 'MAINTAINERS' file.
 
 The mailing lists for the subsystem are damon@lists.linux.dev and
@@ -15,7 +15,7 @@ SCM Trees
 
 There are multiple Linux trees for DAMON development.  Patches under
 development or testing are queued in damon/next [2]_ by the DAMON maintainer.
-Suffieicntly reviewed patches will be queued in mm-unstable [1]_ by the memory
+Sufficiently reviewed patches will be queued in mm-unstable [1]_ by the memory
 management subsystem maintainer.  After more sufficient tests, the patches will
 be queued in mm-stable [3]_ , and finally pull-requested to the mainline by the
 memory management subsystem maintainer.
-- 
2.25.1

[PATCH 03/10] Docs/mm/damon/design: add a section for overall architecture

[SeongJae Park]

The design doc is missing overall picture of DAMON.  Add a section for
overall architeucture and layers.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 0cff6fac6b7e..3b4ce873fa71 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -4,6 +4,21 @@
 Design
 ======
 
+
+Overall Architecture
+====================
+
+DAMON subsystem is configured with three layers including
+
+- Operations Set: Implements fundamental operations for DAMON that depends on
+  the given monitoring target address-space and available set of
+  software/hardware primitives,
+- Core: Implements core logics including monitoring overhead/accurach control
+  and access-aware system operations on top of the operations set layer, and
+- Modules: Implements kernel modules for various purposes that provides
+  interfaces for the user space, on top of the core layer.
+
+
 Configurable Layers
 ===================
 
-- 
2.25.1

[PATCH 04/10] Docs/mm/damon/design: update the layout based on the layers

[SeongJae Park]

DAMON design document is describing only the operations set layer and
monitoring part of the core logic.  Update the layout based on the
DAMON's layers, so that more parts of DAMON including DAMOS core logic
and DAMON modules can easily be added.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 3b4ce873fa71..eaf52f3a9144 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -19,8 +19,8 @@ DAMON subsystem is configured with three layers including
   interfaces for the user space, on top of the core layer.
 
 
-Configurable Layers
-===================
+Configurable Operations Set
+---------------------------
 
 DAMON provides data access monitoring functionality while making the accuracy
 and the overhead controllable.  The fundamental access monitorings require
@@ -42,8 +42,8 @@ Also, if some architectures or devices support special optimized access check
 primitives, those will be easily configurable.
 
 
-Reference Implementations of Address Space Specific Monitoring Operations
-=========================================================================
+Operations Set Layer
+====================
 
 The monitoring operations are defined in two parts:
 
@@ -105,8 +105,12 @@ conflict with the reclaim logic using ``PG_idle`` and ``PG_young`` page flags,
 as Idle page tracking does.
 
 
-Address Space Independent Core Mechanisms
-=========================================
+Core Logics
+===========
+
+
+Monitoring
+----------
 
 Below four sections describe each of the DAMON core mechanisms and the five
 monitoring attributes, ``sampling interval``, ``aggregation interval``,
@@ -115,7 +119,7 @@ regions``.
 
 
 Access Frequency Monitoring
----------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The output of DAMON says what pages are how frequently accessed for a given
 duration.  The resolution of the access frequency is controlled by setting
@@ -142,7 +146,7 @@ size of the target workload grows.
 
 
 Region Based Sampling
----------------------
+~~~~~~~~~~~~~~~~~~~~~
 
 To avoid the unbounded increase of the overhead, DAMON groups adjacent pages
 that assumed to have the same access frequencies into a region.  As long as the
@@ -159,7 +163,7 @@ assumption is not guaranteed.
 
 
 Adaptive Regions Adjustment
----------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Even somehow the initial monitoring target regions are well constructed to
 fulfill the assumption (pages in same region have similar access frequencies),
@@ -178,7 +182,7 @@ keeping the bounds users set for their trade-off.
 
 
 Dynamic Target Space Updates Handling
--------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The monitoring target address range could dynamically changed.  For example,
 virtual memory could be dynamically mapped and unmapped.  Physical memory could
-- 
2.25.1

[PATCH 05/10] Docs/mm/damon/design: rewrite configurable layers

[SeongJae Park]

The 'Configurable Operations Set' section is a little bit outdated.
Update the text.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index eaf52f3a9144..4a22bab124cf 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -22,24 +22,23 @@ DAMON subsystem is configured with three layers including
 Configurable Operations Set
 ---------------------------
 
-DAMON provides data access monitoring functionality while making the accuracy
-and the overhead controllable.  The fundamental access monitorings require
-primitives that dependent on and optimized for the target address space.  On
-the other hand, the accuracy and overhead tradeoff mechanism, which is the core
-of DAMON, is in the pure logic space.  DAMON separates the two parts in
-different layers and defines its interface to allow various low level
-primitives implementations configurable with the core logic.  We call the low
-level primitives implementations monitoring operations.
-
-Due to this separated design and the configurable interface, users can extend
-DAMON for any address space by configuring the core logics with appropriate
-monitoring operations.  If appropriate one is not provided, users can implement
-the operations on their own.
+For data access monitoring and additional low level work, DAMON needs a set of
+implementations for specific operations that are dependent on and optimized for
+the given target address space.  On the other hand, the accuracy and overhead
+tradeoff mechanism, which is the core logic of DAMON, is in the pure logic
+space.  DAMON separates the two parts in different layers, namely DAMON
+Operations Set and DAMON Core Logics Layers, respectively.  It further defines
+the interface between the layers to allow various operations sets to be
+configured with the core logic.
+
+Due to this design, users can extend DAMON for any address space by configuring
+the core logic to use the appropriate operations set.  If any appropriate set
+is unavailable, users can implement one on their own.
 
 For example, physical memory, virtual memory, swap space, those for specific
 processes, NUMA nodes, files, and backing memory devices would be supportable.
-Also, if some architectures or devices support special optimized access check
-primitives, those will be easily configurable.
+Also, if some architectures or devices supporting special optimized access
+check primitives, those will be easily configurable.
 
 
 Operations Set Layer
-- 
2.25.1

[PATCH 06/10] Docs/mm/damon/design: add a section for the relation between Core and Modules layer

[SeongJae Park]

Add overall desription of the interface and the relation between the
Core and the Modules layer under 'Overall Architecture' section.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 4a22bab124cf..41abd0430dd7 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -41,6 +41,16 @@ Also, if some architectures or devices supporting special optimized access
 check primitives, those will be easily configurable.
 
 
+Programmable Modules
+--------------------
+
+Core layer of DAMON is implemented as a framework, and exposes its application
+programming interface to all kernel space components such as subsystems and
+modules.  For common use cases of DAMON, DAMON subsystem provides kernel
+modules that built on top of the core layer using the API, which can be easily
+used by the user space end users.
+
+
 Operations Set Layer
 ====================
 
-- 
2.25.1

[PATCH 07/10] Docs/mm/damon/design: add sections for basic parts of DAMOS

[SeongJae Park]

DAMOS is an important part of DAMON, but the design doc is not covering
it.  Add sections for covering the basic part of DAMOS.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 70 +++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 41abd0430dd7..9f9253529c3d 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -202,3 +202,73 @@ monitoring operations to check dynamic changes including memory mapping changes
 and applies it to monitoring operations-related data structures such as the
 abstracted monitoring target memory area only for each of a user-specified time
 interval (``update interval``).
+
+
+Operation Schemes
+-----------------
+
+One common purpose of data access monitoring is access-aware system efficiency
+optimizations.  For example,
+
+    paging out memory regions that are not accessed for more than two minutes
+
+or
+
+    using THP for memory regions that are larger than 2 MiB and showing a high
+    access frequency for more than one minute.
+
+One straightforward approach for such schemes would be profile-guided
+optimizations.  That is, getting data access monitoring results of the
+workloads or the system using DAMON, finding memory regions of special
+characteristics by profiling the monitoring results, and making system
+operation changes for the regions.  The changes could be made by modifying or
+providing advice to the software (the application and/or the kernel), or
+reconfiguring the hardware.  Both offline and online approaches could be
+available.
+
+Among those, providing advice to the kernel at runtime would be flexible and
+effective, and therefore widely be used.   However, implementing such schemes
+could impose unnecessary redundancy and inefficiency.  The profiling could be
+redundant if the type of interest is common.  Exchanging the information
+including monitoring results and operation advice between kernel and user
+spaces could be inefficient.
+
+To allow users to reduce such redundancy and inefficiencies by offloading the
+works, DAMON provides a feature called Data Access Monitoring-based Operation
+Schemes (DAMOS).  It lets users specify their desired schemes at a high
+level.  For such specifications, DAMON starts monitoring, finds regions having
+the access pattern of interest, and applies the user-desired operation actions
+to the regions as soon as found.
+
+
+Operation Action
+~~~~~~~~~~~~~~~~
+
+The management action that the users desire to apply to the regions of their
+interest.  For example, paging out, prioritizing for next reclamation victim
+selection, advising ``khugepaged`` to collapse or split, or doing nothing but
+collecting statistics of the regions.
+
+The list of supported actions is defined in DAMOS, but the implementation of
+each action is in the DAMON operations set layer because the implementation
+normally depends on the monitoring target address space.  For example, the code
+for paging specific virtual address ranges out would be different from that for
+physical address ranges.  And the monitoring operations implementation sets are
+not mandated to support all actions of the list.  Hence, the availability of
+specific DAMOS action depends on what operations set is selected to be used
+together.
+
+Applying an action to a region is considered as changing the region's
+characteristics.  Hence, DAMOS resets the age of regions when an action is
+applied to those.
+
+
+Target Access Pattern
+~~~~~~~~~~~~~~~~~~~~~
+
+The access pattern of the schemes' interest.  The patterns are constructed with
+the properties that DAMON's monitoring results provide, specifically the size,
+the access frequency, and the age.  Users can describe their access pattern of
+interest by setting minimum and maximum values of the three properties.  If a
+region's three properties are in the ranges, DAMOS classifies it as one of the
+regions that the scheme is having an interest in.
-- 
2.25.1

[PATCH 08/10] Docs/mm/damon/design: add sections for advanced features of DAMOS

[SeongJae Park]

Add sections for advanced features of DAMOS including quotas,
prioritization, watermarks, and filters of DAMOS on the design document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 86 +++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 9f9253529c3d..706dbc17c6cb 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -272,3 +272,89 @@ the access frequency, and the age.  Users can describe their access pattern of
 interest by setting minimum and maximum values of the three properties.  If a
 region's three properties are in the ranges, DAMOS classifies it as one of the
 regions that the scheme is having an interest in.
+
+
+Quotas
+~~~~~~
+
+DAMOS upper-bound overhead control feature.  DAMOS could incur high overhead if
+the target access pattern is not properly tuned.  For example, if a huge memory
+region having the access pattern of interest is found, applying the scheme's
+action to all pages of the huge region could consume unacceptably large system
+resources.  Preventing such issues by tuning the access pattern could be
+challenging, especially if the access patterns of the workloads are highly
+dynamic.
+
+To mitigate that situation, DAMOS provides an upper-bound overhead control
+feature called quotas.  It lets users specify an upper limit of time that DAMOS
+can use for applying the action, and/or a maximum bytes of memory regions that
+the action can be applied within a user-specified time duration.
+
+
+Prioritization
+^^^^^^^^^^^^^^
+
+A mechanism for making a good decision under the quotas.  When the action
+cannot be applied to all regions of interest due to the quotas, DAMOS
+prioritizes regions and applies the action to only regions having high enough
+priorities so that it will not exceed the quotas.
+
+The prioritization mechanism should be different for each action.  For example,
+rarely accessed (colder) memory regions would be prioritized for page-out
+scheme action.  In contrast, the colder regions would be deprioritized for huge
+page collapse scheme action.  Hence, the prioritization mechanisms for each
+action are implemented in each DAMON operations set, together with the actions.
+
+Though the implementation is up to the DAMON operations set, it would be common
+to calculate the priority using the access pattern properties of the regions.
+Some users would want the mechanisms to be personalized for their specific
+case.  For example, some users would want the mechanism to weigh the recency
+(``age``) more than the access frequency (``nr_accesses``).  DAMOS allows users
+to specify the weight of each access pattern property and passes the
+information to the underlying mechanism.  Nevertheless, how and even whether
+the weight will be respected are up to the underlying prioritization mechanism
+implementation.
+
+
+Watermarks
+~~~~~~~~~~
+
+Conditional DAMOS (de)activation automation.  Users might want DAMOS to run
+only under certain situations.  For example, when a sufficient amount of free
+memory is guaranteed, running a scheme for proactive reclamation would only
+consume unnecessary system resources.  To avoid such consumption, the user would
+need to manually monitor some metrics such as free memory ratio, and turn
+DAMON/DAMOS on or off.
+
+DAMOS allows users to offload such works using three watermarks.  It allows the
+users to configure the metric of their interest, and three watermark values,
+namely high, middle, and low.  If the value of the metric becomes above the
+high watermark or below the low watermark, the scheme is deactivated.  If the
+metric becomes below the mid watermark but above the low watermark, the scheme
+is activated.  If all schemes are deactivated by the watermarks, the monitoring
+is also deactivated.  In this case, the DAMON worker thread only periodically
+checks the watermarks and therefore incurs nearly zero overhead.
+
+
+Filters
+~~~~~~~
+
+Non-access pattern-based target memory regions filtering.  If users run
+self-written programs or have good profiling tools, they could know something
+more than the kernel, such as future access patterns or some special
+requirements for specific types of memory. For example, some users may know
+only anonymous pages can impact their program's performance.  They can also
+have a list of latency-critical processes.
+
+To let users optimize DAMOS schemes with such special knowledge, DAMOS provides
+a feature called DAMOS filters.  The feature allows users to set an arbitrary
+number of filters for each scheme.  Each filter specifies the type of target
+memory, and whether it should exclude the memory of the type (filter-out), or
+all except the memory of the type (filter-in).
+
+As of this writing, anonymous page type and memory cgroup type are supported by
+the feature.  Some filter target types can require additional arguments.  For
+example, the memory cgroup filter type asks users to specify the file path of
+the memory cgroup for the filter.  Hence, users can apply specific schemes to
+only anonymous pages, non-anonymous pages, pages of specific cgroups, all pages
+excluding those of specific cgroups, and any combination of those.
-- 
2.25.1

[PATCH 09/10] Docs/mm/damon/design: add a section for DAMON core API

[SeongJae Park]

Add a section covering the API of DAMON core layer on the design
document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 706dbc17c6cb..0ccdd2f6af9f 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -358,3 +358,15 @@ example, the memory cgroup filter type asks users to specify the file path of
 the memory cgroup for the filter.  Hence, users can apply specific schemes to
 only anonymous pages, non-anonymous pages, pages of specific cgroups, all pages
 excluding those of specific cgroups, and any combination of those.
+
+
+Application Programming Interface
+---------------------------------
+
+The programming interface for kernel space data access-aware applications.
+DAMON is a framework, so it does nothing by itself.  Instead, it only helps
+other kernel components such as subsystems and modules building their data
+access-aware applications using DAMON's core features.  For this, DAMON exposes
+its all features to other kernel components via its application programming
+interface, namely ``include/linux/damon.h``.  Please refer to the API
+:doc:`document </mm/damon/api>` for details of the interface.
-- 
2.25.1

[PATCH 10/10] Docs/mm/damon/design: add a section for the modules layer

[SeongJae Park]

Add a section for covering DAMON modules layer to the design document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 61 +++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 0ccdd2f6af9f..da110e89cab4 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -370,3 +370,64 @@ access-aware applications using DAMON's core features.  For this, DAMON exposes
 its all features to other kernel components via its application programming
 interface, namely ``include/linux/damon.h``.  Please refer to the API
 :doc:`document </mm/damon/api>` for details of the interface.
+
+
+Modules
+=======
+
+Because the core of DAMON is a framework for kernel components, it doesn't
+provide any direct interface for the user space.  Such interfaces should be
+implemented by each DAMON API user kernel components, instead.  DAMON subsystem
+itself implements such DAMON API user modules, which are supposed to be used
+for general purpose DAMON control and special purpose data access-aware system
+operations, and provides stable application binary interfaces (ABI) for the
+user space.  The user space can build their efficient data access-aware
+applications using the interfaces.
+
+
+General Purpose User Interface Modules
+--------------------------------------
+
+DAMON modules that provide user space ABIs for general purpose DAMON usage in
+runtime.
+
+DAMON user interface modules, namely 'DAMON sysfs interface' and 'DAMON debugfs
+interface' are DAMON API user kernel modules that provide ABIs to the
+user-space.  Please note that DAMON debugfs interface is currently deprecated.
+
+Like many other ABIs, the modules create files on sysfs and debugfs, allow
+users to specify their requests to and get the answers from DAMON by writing to
+and reading from the files.  As a response to such I/O, DAMON user interface
+modules control DAMON and retrieve the results as user requested via the DAMON
+API, and return the results to the user-space.
+
+The ABIs are designed to be used for user space applications development,
+rather than human beings' fingers.  Human users are recommended to use such
+user space tools.  One such Python-written user space tool is available at
+Github (https://github.com/awslabs/damo), Pypi
+(https://pypistats.org/packages/damo), and Fedora
+(https://packages.fedoraproject.org/pkgs/python-damo/damo/).
+
+Please refer to the ABI :doc:`document </admin-guide/mm/damon/usage>` for
+details of the interfaces.
+
+
+Special-Purpose Access-aware Kernel Modules
+-------------------------------------------
+
+DAMON modules that provide user space ABI for specific purpose DAMON usage.
+
+DAMON sysfs/debugfs user interfaces are for full control of all DAMON features
+in runtime.  For each special-purpose system-wide data access-aware system
+operations such as proactive reclamation or LRU lists balancing, the interfaces
+could be simplified by removing unnecessary knobs for the specific purpose, and
+extended for boot-time and even compile time control.  Default values of DAMON
+control parameters for the usage would also need to be optimized for the
+purpose.
+
+To support such cases, yet more DAMON API user kernel modules that provide more
+simple and optimized user space interfaces are available.  Currently, two
+modules for proactive reclamation and LRU lists manipulation are provided.  For
+more detail, please read the usage documents for those
+(:doc:`/admin-guide/mm/damon/reclaim` and
+:doc:`/admin-guide/mm/damon/lru_sort`).
-- 
2.25.1

Re: [PATCH 00/10] Docs/mm/damon: Minor fixes and design doc update

[SeongJae Park]

On Thu, 25 May 2023 21:43:04 +0000 SeongJae Park <sj@kernel.org> wrote:

> Some of DAMON documents are outdated, or having minor typos or grammar
> erros.  Especially, the design doc has not updated for DAMOS, which is
> an important part of DAMON.  Fix the minor issues and update documents.

By the way, I started writing this patchset before LSFMM, but Michal's feedback
about DAMON documentation has definitely motivated this work, and was helpful.
Thank you, Michal.  I just wanted to say that.  Of course, more documentation
improvement works will be continued.


Thanks,
SJ

> 
> SeongJae Park (10):
>   Docs/mm/damon/faq: remove old questions
>   Docs/mm/damon/maintainer-profile: fix typos and grammar errors
>   Docs/mm/damon/design: add a section for overall architecture
>   Docs/mm/damon/design: update the layout based on the layers
>   Docs/mm/damon/design: rewrite configurable layers
>   Docs/mm/damon/design: add a section for the relation between Core and
>     Modules layer
>   Docs/mm/damon/design: add sections for basic parts of DAMOS
>   Docs/mm/damon/design: add sections for advanced features of DAMOS
>   Docs/mm/damon/design: add a section for DAMON core API
>   Docs/mm/damon/design: add a section for the modules layer
> 
>  Documentation/mm/damon/design.rst             | 309 ++++++++++++++++--
>  Documentation/mm/damon/faq.rst                |  23 --
>  Documentation/mm/damon/maintainer-profile.rst |   4 +-
>  3 files changed, 285 insertions(+), 51 deletions(-)
> 
> -- 
> 2.25.1
>