Add a section for covering DAMON modules layer to the design document. Signed-off-by: SeongJae Park <sj@xxxxxxxxxx> --- 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
