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Docs/mm/damon/design: document node_mem_{used,free}_bp
Add description of DAMOS quota goal metrics for NUMA node utilization on
the DAMON deesign document.
Link: https://lkml.kernel.org/r/20250420194030.75838-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Yunjeong Mun <yunjeong.mun@sk.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
authored by
SeongJae Park
and committed by
Andrew Morton
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Documentation/mm/damon/design.rst
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Documentation/mm/damon/design.rst
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is under achieving the goal, DAMOS automatically increases the quota. If DAMOS
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is over achieving the goal, it decreases the quota.
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The goal can be specified with three parameters, namely ``target_metric``,
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``target_value``, and ``current_value``. The auto-tuning mechanism tries to
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make ``current_value`` of ``target_metric`` be same to ``target_value``.
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Currently, two ``target_metric`` are provided.
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The goal can be specified with four parameters, namely ``target_metric``,
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``target_value``, ``current_value`` and ``nid``. The auto-tuning mechanism
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tries to make ``current_value`` of ``target_metric`` be same to
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``target_value``.
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- ``user_input``: User-provided value. Users could use any metric that they
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has interest in for the value. Use space main workload's latency or
···
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in microseconds that measured from last quota reset to next quota reset.
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DAMOS does the measurement on its own, so only ``target_value`` need to be
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set by users at the initial time. In other words, DAMOS does self-feedback.
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- ``node_mem_used_bp``: Specific NUMA node's used memory ratio in bp (1/10,000).
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- ``node_mem_free_bp``: Specific NUMA node's free memory ratio in bp (1/10,000).
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``nid`` is optionally required for only ``node_mem_used_bp`` and
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``node_mem_free_bp`` to point the specific NUMA node.
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To know how user-space can set the tuning goal metric, the target value, and/or
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the current value via :ref:`DAMON sysfs interface <sysfs_interface>`, refer to