Commit 1b2b7a17 authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
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Docs/admin-guide/mm/damon/usage: document damos_before_apply tracepoint 

Document damos_before_apply tracepoint on the usage document.

Link: https://lkml.kernel.org/r/20230913022050.2109-3-sj@kernel.org


Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c603c630

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

+30 −7
Original line number Diff line number Diff line
@@ -496,15 +496,24 @@ the files as above. Above is only for an example. 


.. _tracepoint:



Tracepoint for Monitoring Results

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

Tracepoints 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::

<sysfs_schemes_tried_regions>`.  The interface is useful for getting a

snapshot, but it could be inefficient for fully recording all the monitoring

results.  For the purpose, two trace points, namely ``damon:damon_aggregated``

and ``damon:damos_before_apply``, are provided.  ``damon:damon_aggregated``

provides the whole monitoring results, while ``damon:damos_before_apply``

provides the monitoring results for regions that each DAMON-based Operation

Scheme (:ref:`DAMOS <damon_design_damos>`) is gonna be applied.  Hence,

``damon:damos_before_apply`` is more useful for recording internal behavior of

DAMOS, or DAMOS target access

:ref:`pattern <damon_design_damos_access_pattern>` based query-like efficient

monitoring results recording.



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 &
@@ -527,6 +536,20 @@ counter). Finally the tenth field (``X``) shows the ``age`` of the region 
(refer to :ref:`design <damon_design_age_tracking>` for more details of the

counter).



If the event was ``damon:damos_beofre_apply``, the ``perf script`` output would

be somewhat like below::



    kdamond.0 47293 [000] 80801.060214: damon:damos_before_apply: ctx_idx=0 scheme_idx=0 target_idx=0 nr_regions=11 121932607488-135128711168: 0 136

    [...]



Each line of the output represents each monitoring region that each DAMON-based

Operation Scheme was about to be applied at the traced time.  The first five

fields are as usual.  It shows the index of the DAMON context (``ctx_idx=X``)

of the scheme in the list of the contexts of the context's kdamond, the index

of the scheme (``scheme_idx=X``) in the list of the schemes of the context, in

addition to the output of ``damon_aggregated`` tracepoint.





.. _debugfs_interface:



debugfs Interface (DEPRECATED!)