Collect entities when a new node entity is added/removed#5
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MartinCornelis2 merged 2 commits intonobleo:nobleo/feature/static_executorfrom Mar 11, 2020
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March 3, 2020 18:29
wait_set_.size_of_* is always different than '0' if we are inside the for loop Signed-off-by: Mauro <mpasserino@irobot.com>
Now we check ONLY node guard_conditions_ Some possible guard conditions to be triggered HERE are: 1. Ctrl+C guard condition 2. Executor interrupt_guard_condition_ 3. Node guard_conditions_ 4. Waitables guard conditions 5. ..more The previous approach was only checking if NOT (1 & 2), so if a Waitable was triggered, it would re-collect all entities, even if no new node entity was added. This was the case of the intra process manager, who relies on waitables. Every time a subscriber got a message, all the entities were collected. Signed-off-by: Mauro <mpasserino@irobot.com>
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The static executor has a list which contains executables like timers, subscribers and waitables belonging to nodes registered in the executor.
This list should be rebuilt each time a new entity is added/removed to/from a node, so the static executor checks for guard conditions being triggered in order to re-collect entities.
Some possible guard conditions to be checked by the static executor are:
The previous approach was only checking if NOT (1 & 2), so if a waitable guard condition was triggered it would re-collect all entities, even if no new node entities were added/removed.
This is the case of the intra process manager, which relies on waitables. Every time a subscriber gets a message, all the entities would be re-collected in the executable list. This could happen hundreds of times per second, having a noticeable impact on the CPU performance and in the ROS2 system (high latencies, lost messages).
With the new approach the executable list is rebuilt only when a new node entity is added/removed to/from a node, by checking for triggered guard conditions belonging to nodes registered in the executor.
Below, the benchmark [1] performances for the standard, static and modified static executor on a Rasperry Pi Model A+ (RPi 1), single core @700Mhz
Using:
The gain in CPU performance is about ~13% compared to the StaticSingleThreadedExecutor, and 32% compared to the SingleThreadedExecutor.
@alsora
@dgoel
[1] https://github.com/irobot-ros/ros2-performance/tree/master/performances/benchmark