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

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

Resource limit	Size in Bytes	Notes
DomainParticipantFactory	2512
max_participants	15558	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	140	Add strlen(topic_name) + 1
local_type_allocation	36	Add strlen(type_name) + 1
local_publisher_allocation	268
local_subscriber_allocation	268
local_reader_allocation	2285	The sample and instance resources must be added.
local_writer_allocation	2727	The sample and instance resources must be added.
matching_writer_reader_pair_allocation	28
remote_participant_allocation	905
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	376
(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 Best Effort) max_instances	80
(DataWriter Best Effort) max_samples	116
(DataWriter Best Effort) max_remote_readers	391
(DataWriter Best Effort) max_routes_per_reader	87
(DataWriter Reliable) max_instances	79
(DataWriter Reliable) max_samples	480
(DataWriter Reliable) max_remote_readers	391
(DataWriter Reliable) 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

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

9.3.1.1.2. Topic

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

9.3.1.1.3. DDS DataReader

(2285) + (rl_ms * 160 ) + (rl_mi * 271) + (rl_mrw * 391) + (rl_mrpw * 87)

9.3.1.1.4. DDS DataWriter

(2727) + (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	66488

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	32020