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Docs/admin-guide/mm/damon/usage: document damos_before_apply tracepoint

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Document damos_before_apply tracepoint on the usage document.

Link: https://lkml.kernel.org/r/20230913022050.2109-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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SeongJae Park 2023-09-13 02:20:50 +00:00 committed by Andrew Morton
parent c603c630b5
commit 1b2b7a17ab
1 changed files with 30 additions and 7 deletions
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37
Documentation/admin-guide/mm/damon/usage.rst
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@ -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!)