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How the Nasal GC works: Difference between revisions
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The [[Nasal]] language is a dynamic programming language, where memory is not manually allocated and freed by the programmer, but instead the Nasal virtual machine automatically allocates memory from so called "memory pools", every so often these memory pools must be checked, to see how many references (i.e. objects like variables) are still reachable, so that the unreachable ones can be removed from the memory pool and/or so that memory blocks in each pool can be allocated or freed. This is called "garbage management" or "garbage collection". | The [[Nasal]] language is a dynamic programming language, where memory is not manually allocated and freed by the programmer, but instead the Nasal virtual machine automatically allocates memory from so called "memory pools", every so often these memory pools must be checked, to see how many references (i.e. objects like variables) are still reachable, so that the unreachable ones can be removed from the memory pool and/or so that memory blocks in each pool can be allocated or freed. This is called "garbage management" or "garbage collection". | ||
The current Nasal garbage collector (GC) is known to affect the frame rate in FlightGear and occasionally causes stutter (increased frame spacing) under certain circumstances. This is largely attributed to | The current Nasal garbage collector (GC) is known to affect the frame rate in FlightGear and occasionally causes stutter (increased frame spacing) under certain circumstances (i.e. under heavy load, due to complex scripts - such as the [[Bombable]] addon or the local weather system. | ||
This is largely attributed to the GC being a fairly simple sequential [http://en.wikipedia.org/wiki/Garbage_collection_(computer_science)#Copying_vs._mark-and-sweep_vs._mark-and-don.27t-sweep mark/sweep collector], which needs to stop all operations, mark all reachable objects and free unreachable objects in an exclusive, single-threaded, fashion. | |||
In other words, the time spent in the GC is proportial to the number of active objects (i.e. lines of code), even for objects which may not be running or active - just loaded. For additional background information, please see [[Improving Nasal]]. | In other words, the time spent in the GC is proportial to the number of active objects (i.e. lines of code), even for objects which may not be running or active - just loaded. For additional background information, please see [[Improving Nasal]]. | ||