Issues with the 'CPU time' limit

[GraphR00t]

The CPU time limit limits the amount of CPU time spent by a module and its children.

• This limit is NOT intended to be very precise.
• The total work done by an Inox process should not be computed based on CPU time spent by all modules running in the process.

Main Issues

• When a goroutine (module) pauses its execution its CPU time bucket does not stop decreasing the token count, unless the code section that causes the goroutine switch is wrapped in a Context.DoIO call. Goroutines can also be preempted.
• Some goroutines do not correspond to a module, therefore the CPU time they spend is not counted.

Preemption

Proposed solutions (should be used in conjunction)

• Wrap as many code snippets as possible that can cause a goroutine switch in a Context.DoIO call, although this is very limited.
• Make lthreads periodically report to their CPU-time limiter that they are running, this should be implemented in several places.
  • In the evaluation loop
  • In several points of long-running sections of Go-only code
• Avoid doing heavy work in independent goroutines.