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SharedReaderQueue Resource Management
❏ max_in_memory_bytes: LENGTH_UNLIMITED or positive number
Defaults:
❏ max_in_memory_bytes: LENGTH_UNLIMITED
2.15.2
Memory Management for a Sample
For every sample in a SharedReaderQueue, Queuing Service will use a buffer to store the content
of the sample in serialized form. The memory for that buffer may come from a pre-allocated
pool of buffers or may be dynamically allocated from the heap upon sample reception. This
behavior is controlled per <domain_participant> using the XML tag <memory_management>
(see Table 3.10, DomainParticipant Tags), which affects all the SharedReaderQueues within the
<domain_participant>.
For example:
<memory_management>
<sample_buffer_min_size>16000</sample_buffer_min_size>
<sample_buffer_trim_to_size>true</sample_buffer_trim_to_size>
</memory_management>
In the above example:
❏ sample_buffer_min_size: If the serialized size of an incoming sample is smaller or equal
to 16000 bytes, Queuing Service will use a pre-allocated buffer from a pool to hold the
sample. The initial and maximum number of buffers in the pool as well as the pool’s
growth policy is configured using the XML tag <resource_limits> under
<shared_reader_queue>/<queue_qos>. When the serialized size of the incoming sample
is greater than 16,000 bytes, Queuing Service will allocate the buffer from the heap dynamically upon sample reception.
❏ sample_buffer_trim_to_size: For dynamically allocated buffers Queuing Service will
release the memory after the sample is removed from the SharedReaderQueue.
For more information on <memory_management> and its default values, see Table 3.10,
DomainParticipant Tags.
2.15.3
High and Low Watermarks
The tag <queue_watermark_settings> under <shared_reader_queue>/<queue_qos>/
<resource_limits> can be used to configure high and low watermarks in a SharedReaderQueue
(see Table 3.15, Queue QoS Tags). Watermarks are expressed as a percentage with respect to the
maximum number of samples or maximum number of bytes allowed in the SharedReaderQueue. For example:
<resource_limits>
<queue_allocation_settings>
<max_count>1000</max_count>
<max_in_memory_bytes>10000000</max_in_memory_bytes>
</queue_allocation_settings>
<queue_watermark_settings>
<high_watermark>90</low_watermark>
<low_watermark>10</low_watermark>
</queue_watermark_settings>
</resource_limits>
In the above example, the high watermark of 90% corresponds to 900 samples (9,000,000 bytes)
and the low watermark of 10% corresponds to 100 samples (1,000,000 bytes).
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