diff options
| -rw-r--r-- | Documentation/mm/damon/design.rst | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst index fa7392b5a331..6731c3102d0f 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -276,6 +276,43 @@ interval``, DAMON checks if the region's size and access frequency (``nr_accesses``) has significantly changed. If so, the counter is reset to zero. Otherwise, the counter is increased. +Data Attributes Monitoring +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Data access pattern is only one type of data attributes. In some use cases, +users need to know more data attributes information. For example, users may +need to know how much of a given hot or cold memory region is backed by +anonymous pages, or belong to a specific cgroup. For such use case, data +attributes monitoring feature is provided. + +Using the feature, users can register data attributes of their interest to the +DAMON :ref:`context <damon_design_execution_model_and_data_structures>`. The +registration is made by specifying a probe per attribute. Each of the probe +specifies a rule to determine if a given memory region has the related +attribute. The rule is constructed with multiple filters. The filters work +same to :ref:`DAMOS filters <damon_design_damos_filters>` except the supported +filter types. Currently only ``anon`` filter type is supported for data +attributes monitoring. + +If such probes are registered, DAMON executes the probes for each region's +sampling memory when it does the access :ref:`sampling +<damon_design_region_based_sampling>`. The number of samples that identified +as having the data attribute (hitting the probe) per :ref:`aggregation interval +<damon_design_monitoring>` is accounted in a per-region per-probe counter. +Users can therefore know how much of a given DAMON region has a specific data +attribute by reading the per-region per-probe probe hits counter after each +aggregation interval. + +This is a sampling based mechanism. Hence, it is lightweight but the output +may include some measurement errors. The output should be used with good +understanding of statistics. + +Another way to do this for higher accuracy is using :ref:`DAMOS filter +<damon_design_damos_filters>` with ``stat`` :ref:`action +<damon_design_damos_action>` and ``sz_ops_filter_passed`` :ref:`stat +<damon_design_damos_stat>`. This approach provides the data attributes +information in page level. But, because it is operated in page level, the +overhead is proportional to the size of the memory. Dynamic Target Space Updates Handling ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |