Reduce ROS2 memory usage

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Hi,

I noticed that the memory used by a ROS2 process is really high.

For example running psrecord

$ psrecord --plot listener.png --include-children --duration 10 "ros2 run demo_nodes_cpp listener"

The result will show that a node with only a subscription to a String topic has a memory usage of more than 55 MB. The same amount of memory can be checked using tools like free.

Running the same test with a different node

$ psrecord --plot listener.png --include-children --duration 10 "ros2 run image_tools showimage"

This executable instantiates a subscriber for images, resulting in more than 80 MB of memory.

Are these results consistent with your experience or am I doing something wrong? Is there a way to reduce the ROS2 memory usage?

EDIT: I noticed that part of this memory is due to the execution of the node using the ROS2 CLI, the memory usage reduces when directly calling ./EXECUTABLE_NAME.

EDIT: I have further investigated this issue using valgrind. Thus, without considering the ROS2 CLI process or other things, creating a node with a subscription to an INT64 topic will allocate approx 14 MB. Then I tried creating messages with bigger size (i.e. 0.01 MB, 1 MB, 2 MB, 4MB) and I found a dramatic proportion.

Array4MB.msg

byte[4000000] array

The memory allocated for a node with a subscription is approximately 200 TIMES the dimension of the message. Creating a node which subscribes to a topic where messages of fixed size 4 MB are published, will allocate 800 MB!!

I'm only instantiating the node, it's not spinning or doing anything else.

Thank you