9.3. Heap Benchmarks

The “Heap” section provides information about how much dynamically allocated memory is used by Connext DDS Micro. It should be noted that exact numbers are very difficult to estimate and that the numbers are only for guidance. Please refer to ResourceModule for a more information on resource-limits and memory usage.

On Linux, for each heap allocation using malloc, malloc_usable_size() is called to determine the actual size of each allocation. The numbers include resources used by the RH_SM, WH_SM, and UDP components, but not the resources used by the dynamic discovery component (DPDE) or the static discovery component (DPSE). In addition, please note that the memory does not include memory for the actual user-data. This must be added according to the resource-limits. The numbers are for the release libraries.

The size for entities that are controlled by resource-limits are provided. In addition, a formula is provided to estimate the amount of memory used by a data reader and data writer as these are typically the ones that consume most of the memory.

9.3.1. Heap Usage

../_images/MicroMemoryMap.png

The following table shows how much memory each resource-limit in the memory model

Resource-limit Size in Bytes Notes
DomainParticipantFactory 2184  
max_participants 13712 This is the memory for an empty participant. The memory used by each entity must be added as described for each entity.
max_components N/A  
local_topic_allocation 116 Add strlen(topic_name) + 1
local_type_allocation 12 Add strlen(type_name) + 1
local_publisher_allocation 268  
local_subscriber_allocation 268  
local_reader_allocation 2184 The sample and instance resources must be added.
local_writer_allocation 2595 The sample and instance resources must be added.
matching_writer_reader_pair_allocation 28  
remote_participant_allocation 500  
remote_writer_allocation about 600 This includes the topic_name
remote_reader_allocation about 600 This includes the topic_name
max_destination_ports 77  
max_receive_ports 360  
(DataReader) max_instances 271  
(DataReader) max_samples 160  
(DataReader) max_remote_writers 391  
(DataReader) max_routes_per_writer 87  
(DataReader) max_samples_per_instance 0  
(DataReader) max_remote_writers_per_instance 0  
(DataReader) max_samples_per_remote_writer 0  
(DataWriter) max_instances 79  
(DataWriter) max_samples 116  
(DataWriter) max_remote_readers 391  
(DataWriter) max_routes_per_reader 87  
(DataWriter) max_samples_per_instance 0  
max_locators_per_discovered_participant 83  
max_buffer_size 0  
max_message_size 0  
matching_reader_writer_pair_allocation 0  

9.3.1.1. Calculating Memory Usage for DDS Entities

The following short-hands are used in these formulas:

  • rl_ms - resource_limits.max_samples
  • rl_mi - resource_limits.max_instances
  • rl_mrw - datareader_resource_limits.max_remote_writers
  • rl_mrpw - datareader_resource_limits.max_routes_per_writer
  • wrl_mrw - datawriter_resource_limits.max_remote_readers
  • wrl_mrpr - datawriter_resource_limits.max_routes_per_reader

9.3.1.1.1. Type

(13) + string.len(type_name) + 1

9.3.1.1.2. Topic

(117) + string.len(topic_name) + 1

9.3.1.1.3. DDS DataReader

(2184) + (rl_ms * 160 ) + (rl_mi * 271) + (rl_mrw * 391) + (rl_mrpw * 87)

9.3.1.1.4. DDS DataWriter

(2595) + (rl_ms * 116) + (rl_mi * 79) + (wrl_mrr * 391) + (wrl_mrpr * 87)

9.3.1.1.5. RemoteParticipant

(501) + (16 * 24)

9.3.1.1.6. RemotePublication

(149) + string.len(topic_name) + 1 + (16 * 24)

9.3.1.1.7. RemoteSubscription

(173) + strlen(topic_name) + 1 + (16 * 24)

9.3.2. Dynamic Discovery (DPDE) Heap Usage Information

The DPDE plugin is a DDS application that advertises locally created DDS entities and listens for DDS entities available in the DDS data-space. It is implemented using the DDS APIs supported by Connext DDS Micro.

The DPDE plugin creates the following DDS entities:

  • One DDS Publisher
  • One DDS Subscriber
  • Three DDS Topics
  • Three DDS DataReaders
  • Three DDS DataWriters

The DPDE plugin also registers the following three types:

  • DDS_ParticipantBuiltinTopicData
  • DDS_PublicationBuiltinTopicData
  • DDS_SubscriptionBuiltinTopicData

All heap memory allocated by the DPDE plugin is allocated after the DDS DomainParticipant is created (no additional memory is allocated after the DDS DomainParticipant is enabled).

DPDE Plugin Release Size(B)
Plugin 65560

9.3.3. Static Discovery (DPSE) Heap Usage Information

The DPSE plugin is a DDS application that only advertises locally created DDS DomainParticipants and listens for other DDS DomainParticipants available in the DDS data-space. It is implemented using the DDS APIs supported by Connext DDS Micro.

The DPSE plugin creates the following DDS entities:

  • One DDS Publisher
  • One DDS Subscriber
  • One DDS Topics
  • One DDS DataReader
  • One DDS DataWriter

The DPSE plugin also registers the following type:

  • DDS_ParticipantBuiltinTopicData

All heap memory allocated by the DPSE plugin is allocated after the DDS DomainParticipant is created (no additional memory is allocated after the DDS DomainParticipant is enabled).

DSDE Plugin Release Size(B)
Plugin 31644