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Docs/admin-guide/mm/damon/usage: document DAMOS filters of sysfs
Document about the newly added files for DAMOS filters on the DAMON usage document. Link: https://lkml.kernel.org/r/20221205230830.144349-11-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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@ -87,6 +87,8 @@ comma (","). ::
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│ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms
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│ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
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│ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low
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│ │ │ │ │ │ │ filters/nr_filters
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│ │ │ │ │ │ │ │ 0/type,matching,memcg_id
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│ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds
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│ │ │ │ │ │ │ tried_regions/
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│ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age
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@ -151,6 +153,8 @@ number (``N``) to the file creates the number of child directories named as
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moment, only one context per kdamond is supported, so only ``0`` or ``1`` can
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be written to the file.
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.. _sysfs_contexts:
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contexts/<N>/
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-------------
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@ -268,8 +272,8 @@ schemes/<N>/
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------------
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In each scheme directory, five directories (``access_pattern``, ``quotas``,
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``watermarks``, ``stats``, and ``tried_regions``) and one file (``action``)
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exist.
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``watermarks``, ``filters``, ``stats``, and ``tried_regions``) and one file
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(``action``) exist.
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The ``action`` file is for setting and getting what action you want to apply to
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memory regions having specific access pattern of the interest. The keywords
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@ -347,6 +351,46 @@ as below.
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The ``interval`` should written in microseconds unit.
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schemes/<N>/filters/
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--------------------
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Users could know something more than the kernel for specific types of memory.
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In the case, users could do their own management for the memory and hence
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doesn't want DAMOS bothers that. Users could limit DAMOS by setting the access
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pattern of the scheme and/or the monitoring regions for the purpose, but that
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can be inefficient in some cases. In such cases, users could set non-access
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pattern driven filters using files in this directory.
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In the beginning, this directory has only one file, ``nr_filters``. Writing a
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number (``N``) to the file creates the number of child directories named ``0``
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to ``N-1``. Each directory represents each filter. The filters are evaluated
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in the numeric order.
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Each filter directory contains three files, namely ``type``, ``matcing``, and
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``memcg_path``. You can write one of two special keywords, ``anon`` for
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anonymous pages, or ``memcg`` for specific memory cgroup filtering. In case of
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the memory cgroup filtering, you can specify the memory cgroup of the interest
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by writing the path of the memory cgroup from the cgroups mount point to
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``memcg_path`` file. You can write ``Y`` or ``N`` to ``matching`` file to
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filter out pages that does or does not match to the type, respectively. Then,
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the scheme's action will not be applied to the pages that specified to be
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filtered out.
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For example, below restricts a DAMOS action to be applied to only non-anonymous
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pages of all memory cgroups except ``/having_care_already``.::
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# echo 2 > nr_filters
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# # filter out anonymous pages
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echo anon > 0/type
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echo Y > 0/matching
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# # further filter out all cgroups except one at '/having_care_already'
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echo memcg > 1/type
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echo /having_care_already > 1/memcg_path
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echo N > 1/matching
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Note that filters could be ignored depend on the running DAMON operations set
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`implementation <sysfs_contexts>`.
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.. _sysfs_schemes_stats:
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schemes/<N>/stats/
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