[FEA] Add support to SCHED DEADLINE realtime control policy.

[ZhenshengLee]

Is your feature request related to a problem? Please describe.

there
are only two viable choices: either use a classic POSIX
fixed-priority scheduler (i.e., the SCHED FIFO or SCHED RR
policies), or rely on Linux’s more recent reservation-based
SCHED DEADLINE scheduler. We chose the latter.

Compared to the fixed-priority option, SCHED DEADLINE
provides two main advantages: analyzability and containment.
Most importantly, its convenient analyzability stems from
the fact that Casini et al.’s response-time analysis for ROS
processing chains

from the paper Automatic Latency Management for ROS 2: Benefits, Challenges, and Open Problems

We can see the advantages of using SCHED DEADLINE policy to control the realtime profile of a thread of ROS2 application.

And currently It is the FIFO policy that is in use in this pendulum demo

pendulum/pendulum_utils/include/pendulum_utils/process_settings.hpp

Line 101 in 1492110

if (set_this_thread_priority(process_priority, SCHED_FIFO)) {

Describe the solution you'd like
add deadline sched functions to pendulum_utilities package.

[carlossvg]

@ZhenshengLee My understanding is that this wouldn't be as simple as adding this policy to set_this_thread_priority, this would require some changes in the application too, isn't it? I will try to reserve some time to evaluate how easy would be to implement this. Please post here any additional resources or examples you are aware. Thanks!