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authorSeongJae Park <sj@kernel.org>2021-11-05 21:46:39 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-06 21:30:44 +0100
commit68536f8e01e571f553f78fa058ba543de3834452 (patch)
tree8f30a62b0e2c7f1f3e90225f298498adc4d01610 /Documentation
parentselftests/damon: add 'schemes' debugfs tests (diff)
downloadlinux-68536f8e01e571f553f78fa058ba543de3834452.tar.xz
linux-68536f8e01e571f553f78fa058ba543de3834452.zip
Docs/admin-guide/mm/damon: document DAMON-based Operation Schemes
This adds the description of DAMON-based operation schemes in the DAMON documents. Link: https://lkml.kernel.org/r/20211001125604.29660-8-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/mm/damon/start.rst11
-rw-r--r--Documentation/admin-guide/mm/damon/usage.rst51
2 files changed, 60 insertions, 2 deletions
diff --git a/Documentation/admin-guide/mm/damon/start.rst b/Documentation/admin-guide/mm/damon/start.rst
index d5eb89a8fc38..51503cf90ca2 100644
--- a/Documentation/admin-guide/mm/damon/start.rst
+++ b/Documentation/admin-guide/mm/damon/start.rst
@@ -108,6 +108,17 @@ the results as separate image files. ::
You can view the visualizations of this example workload at [1]_.
Visualizations of other realistic workloads are available at [2]_ [3]_ [4]_.
+
+Data Access Pattern Aware Memory Management
+===========================================
+
+Below three commands make every memory region of size >=4K that doesn't
+accessed for >=60 seconds in your workload to be swapped out. ::
+
+ $ echo "#min-size max-size min-acc max-acc min-age max-age action" > scheme
+ $ echo "4K max 0 0 60s max pageout" >> scheme
+ $ damo schemes -c my_thp_scheme <pid of your workload>
+
.. [1] https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/start.html#visualizing-recorded-patterns
.. [2] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
.. [3] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index a72cda374aba..c0296c14babf 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -34,8 +34,8 @@ the reason, this document describes only the debugfs interface
debugfs Interface
=================
-DAMON exports three files, ``attrs``, ``target_ids``, and ``monitor_on`` under
-its debugfs directory, ``<debugfs>/damon/``.
+DAMON exports four files, ``attrs``, ``target_ids``, ``schemes`` and
+``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
Attributes
@@ -74,6 +74,53 @@ check it again::
Note that setting the target ids doesn't start the monitoring.
+Schemes
+-------
+
+For usual DAMON-based data access aware memory management optimizations, users
+would simply want the system to apply a memory management action to a memory
+region of a specific size having a specific access frequency for a specific
+time. DAMON receives such formalized operation schemes from the user and
+applies those to the target processes. It also counts the total number and
+size of regions that each scheme is applied. This statistics can be used for
+online analysis or tuning of the schemes.
+
+Users can get and set the schemes by reading from and writing to ``schemes``
+debugfs file. Reading the file also shows the statistics of each scheme. To
+the file, each of the schemes should be represented in each line in below form:
+
+ min-size max-size min-acc max-acc min-age max-age action
+
+Note that the ranges are closed interval. Bytes for the size of regions
+(``min-size`` and ``max-size``), number of monitored accesses per aggregate
+interval for access frequency (``min-acc`` and ``max-acc``), number of
+aggregate intervals for the age of regions (``min-age`` and ``max-age``), and a
+predefined integer for memory management actions should be used. The supported
+numbers and their meanings are as below.
+
+ - 0: Call ``madvise()`` for the region with ``MADV_WILLNEED``
+ - 1: Call ``madvise()`` for the region with ``MADV_COLD``
+ - 2: Call ``madvise()`` for the region with ``MADV_PAGEOUT``
+ - 3: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``
+ - 4: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``
+ - 5: Do nothing but count the statistics
+
+You can disable schemes by simply writing an empty string to the file. For
+example, below commands applies a scheme saying "If a memory region of size in
+[4KiB, 8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate
+interval in [10, 20], page out the region", check the entered scheme again, and
+finally remove the scheme. ::
+
+ # cd <debugfs>/damon
+ # echo "4096 8192 0 5 10 20 2" > schemes
+ # cat schemes
+ 4096 8192 0 5 10 20 2 0 0
+ # echo > schemes
+
+The last two integers in the 4th line of above example is the total number and
+the total size of the regions that the scheme is applied.
+
+
Turning On/Off
--------------