Why Some Programmers Avoid Garbage Collection in Low-Level Programming
Garbage collection (GC) is a form of automatic memory management that frees up memory occupied by unused or unreachable objects. GC is a common feature of many high-level programming languages, such as Java, C#, and Python, that simplifies the development process and reduces the risk of memory leaks and errors. However, not all programmers choose to use GC, especially when they are working with low-level programming languages, such as C, C++, and assembly. What are some of the reasons that might lead a programmer to avoid GC in low-level programming?
One possible reason is performance. GC can introduce overhead and latency to the execution of a program, as it periodically scans the heap for garbage objects and reclaims their memory. This can affect the responsiveness and predictability of the program, especially for real-time or embedded systems that have strict timing constraints. GC can also cause memory fragmentation, as it moves objects around to compact the heap. This can reduce the cache locality and efficiency of the program. Moreover, GC can consume more memory than manual memory management, as it needs to maintain extra data structures and metadata for tracking objects and their references. Therefore, some programmers may prefer to have direct and precise control over the memory allocation and deallocation of their program, and avoid the potential performance penalties of GC.
Some of the performance penalties of GC include the following:
- GC can introduce pauses or suspensions to the execution of the program, as it needs to ensure the integrity of the object trees. This can disrupt the smoothness and continuity of the program, and lead to scalability problems in multithreaded applications.
- GC can have a negative impact on the mutator performance and locality, as it competes with the application for CPU and memory resources. This can degrade the throughput and quality of service of the program, and increase the energy consumption and heat dissipation of the system.
- GC can be unpredictable and non-deterministic, as it depends on various factors such as the heap size, the allocation rate, the live set size, the collector algorithm, and the runtime system. This can make it difficult to tune and optimize the performance of the program, and to meet the deadlines and guarantees of the system.
Another possible reason is compatibility. GC requires support from the compiler and the runtime system of the programming language. However, not all low-level programming languages have such support, or have it only as an optional feature. For example, C and C++ do not have built-in GC, but rely on third-party libraries or frameworks to provide it. Assembly language, which is the lowest level of programming language, does not have any abstraction or support for GC at all. Therefore, some programmers may choose to use manual memory management, as it is more portable and compatible across different platforms and systems.
Some of the compatibility issues of GC include the following:
- GC may not be available or reliable for some platforms or systems, such as embedded devices, real-time systems, or legacy systems. These systems may have limited resources, strict timing requirements, or specific hardware configurations that GC cannot handle or interfere with.
- GC may not be compatible or interoperable with some native or unmanaged code, such as libraries, frameworks, or operating system calls. These code may have different memory management conventions, assumptions, or expectations that GC cannot guarantee or satisfy.
- GC may not be consistent or standardized across different programming languages, compilers, or runtime systems. Different implementations of GC may have different algorithms, parameters, or behaviors that affect the performance, correctness, or portability of the program.
A third possible reason is preference. GC is not a silver bullet that solves all memory management problems. It has its own limitations and trade-offs, such as the difficulty of handling cyclic references, finalization, and resource management. GC also changes the programming paradigm and style, as it abstracts away the memory management details from the programmer. However, some programmers may prefer to have more visibility and responsibility over the memory management of their program, as it gives them more flexibility and expressiveness. They may also enjoy the challenge and satisfaction of writing efficient and correct code without relying on GC.
Some of the preference factors of manual memory management include the following:
- Manual memory management can be easier for the programmer to understand exactly what is going on, as they have to explicitly allocate and deallocate memory for each object.
- Manual memory management can perform better when there is a shortage of memory, as it allows the programmer to optimize the memory usage and avoid unnecessary allocations.
- Manual memory management can be more suitable for some applications that have specific memory management requirements, such as real-time systems, embedded devices, or legacy systems.
In conclusion, GC is a useful and convenient feature of many high-level programming languages, but it is not a necessity or a requirement for low-level programming. Some programmers may choose not to use GC in low-level programming for various reasons, such as performance, compatibility, or preference. Ultimately, the choice of memory management technique depends on the goals, constraints, and preferences of the programmer and the program.
