Commit 995d739c authored by SeongJae Park's avatar SeongJae Park Committed by Linus Torvalds
Browse files

Docs/admin-guide/mm/damon/usage: update for kdamond_pid and (mk|rm)_contexts 

The DAMON debugfs usage document is missing descriptions for
'kdamond_pid', 'mk_contexts', and 'rm_contexts' debugfs files.  This
commit adds those.

Link: https://lkml.kernel.org/r/20211209131806.19317-6-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4492bf45

Documentation/admin-guide/mm/damon/usage.rst

+49 −3
Original line number Diff line number Diff line
@@ -38,9 +38,9 @@ DAMON provides below three interfaces for different users. 
debugfs Interface

=================



DAMON exports five files, ``attrs``, ``target_ids``, ``init_regions``,

``schemes`` and ``monitor_on`` under its debugfs directory,

``<debugfs>/damon/``.

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
@@ -273,6 +273,52 @@ 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