shm transport delay is too large

[zonghai-yang]

Is there an already existing issue for this?

• I have searched the existing issues

Expected behavior

I hope the latency of writing big data is high and the latency of writing small data is low.

Current behavior

I use two processes.Process 1 has two datawriters.Process 2 has two datareaders.The topic of datawriter1 and datareader1 is topic1.
The topic of datawriter2 and datareader2 is topic2.Datawriter1 write a large size msg1.Datawriter2 write a small size msg2.I hope delay of msg1 is long and delay of msg2 is small.But delay of msg2 also long.I think it was influenced by writer1.I changed the sending order of writer1 and writer2 and sent small data first. The latency of small data has become lower。

Steps to reproduce

process_1:
sizeof(msg_1) == 1M;
sizeof(msg_2) == 10byte;
datawriter_1.topic() = "topic_1";
datawriter_2.topic() = "topic_2";
datawriter_1.write(msg_1);
datawriter_2.write(msg_2);
//if write msg_2 first , delay will correct

process_2:
datareader_1.topic() = "topic_1";
datareader_2.topic() = "topic_2";
std::cout<<now - msg_1.timestamp();
std::cout<<now - msg_2.timestamp();

Fast DDS version/commit

v2.11.2

Platform/Architecture

Other. Please specify in Additional context section.

Transport layer

Default configuration, UDPv4 & SHM

Additional context

No response

XML configuration file

No response

Relevant log output

No response

Network traffic capture

No response