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Docs/mm/damon/design: document quota goal self-tuning

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Update DAMON design doc to explain the quota goal self-tuning, which can
be used by setting the goal's metric to metrics that kernel can
self-retrieve.

Link: https://lkml.kernel.org/r/20240219194431.159606-16-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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SeongJae Park 2024-02-19 11:44:26 -08:00 committed by Andrew Morton
parent 4daacfe8f9
commit 3c17174f64
1 changed files with 18 additions and 2 deletions
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20
Documentation/mm/damon/design.rst
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@ -398,12 +398,28 @@ Aim-oriented Feedback-driven Auto-tuning
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Automatic feedback-driven quota tuning. Instead of setting the absolute quota
value, users can repeatedly provide numbers representing how much of their goal
for the scheme is achieved as feedback. DAMOS then automatically tunes the
value, users can specify the metric of their interest, and what target value
they want the metric value to be. DAMOS then automatically tunes the
aggressiveness (the quota) of the corresponding scheme. For example, if DAMOS
is under achieving the goal, DAMOS automatically increases the quota. If DAMOS
is over achieving the goal, it decreases the quota.
The goal can be specified with three parameters, namely ``target_metric``,
``target_value``, and ``current_value``. The auto-tuning mechanism tries to
make ``current_value`` of ``target_metric`` be same to ``target_value``.
Currently, two ``target_metric`` are provided.
- ``user_input``: User-provided value. Users could use any metric that they
has interest in for the value. Use space main workload's latency or
throughput, system metrics like free memory ratio or memory pressure stall
time (PSI) could be examples. Note that users should explicitly set
``current_value`` on their own in this case. In other words, users should
repeatedly provide the feedback.
- ``some_mem_psi_us``: System-wide ``some`` memory pressure stall information
in microseconds that measured from last quota reset to next quota reset.
DAMOS does the measurement on its own, so only ``target_value`` need to be
set by users at the initial time. In other words, DAMOS does self-feedback.
.. _damon_design_damos_watermarks: