golang mallocgc too many

Golang is a very popular programming language. It is accepted by more and more developers for its efficient concurrency design, easy-to-learn syntax and fast compilation speed. However, for some Golang programmers, there is a very thorny problem: too many MallocGCs, causing the program to run inefficiently.

In Golang, memory management is completed by the garbage collector (Garbage Collector, GC), which greatly reduces the burden on programmers. The garbage collector introduced by Golang adopts the Mark and Sweep method. It scans the objects in the memory, marks the objects that need to be recycled, and then clears the unnecessary objects. This method is widely used in other programming languages, such as Java, Python, etc., but in Golang, its implementation is different from other languages.

The triggering mechanism of Golang GC is based on object memory allocation and heap memory size. When memory allocation occurs during program execution, the GC will determine whether the current memory usage exceeds a certain threshold of heap memory. If it exceeds, the GC will be triggered. Of course, this is also one of the problems encountered by many Golang programmers.

On the one hand, MallocGC is closely related to the garbage collection mechanism. Golang establishes a global heap memory based on all M. Back-to-back stack memory is allocated for each Goroutine at runtime. Stack memory management is managed by each Goroutine. When a Goroutine needs to cross stack boundaries, it does so through a mechanism called "cgo call".

On the other hand, due to Golang's memory allocation mechanism, the conditions for Malloc to trigger GC are relatively frequent, and the GC process involves a large number of traversal and copy operations, which is easy to cause problems in scenarios where memory usage is large. Performance issues. For example, when a large number of small or medium-sized objects are allocated and released in a short period of time, the GC will be triggered frequently, thus affecting the performance of the program.

In order to solve this problem, some Golang programmers have proposed some solutions:

1. Use sync.Pool: sync.Pool is a pooling technology provided by Golang that can be repeated Utilize allocated objects to avoid frequent allocation and deallocation of memory. Using sync.Pool can greatly reduce GC frequency.
2. Use slab memory allocator: slab is an efficient memory allocator that pre-allocates large blocks of memory and divides it into small blocks, and then allocates these small blocks to different Goroutines for use. , avoiding frequent memory allocation and recycling.
3. Reduce the frequency of memory allocation: Reduce the frequency of memory allocation as much as possible, especially when a large number of small or medium-sized objects are allocated and released in a short period of time. These objects can be placed in a cache pool to avoid frequent Create and destroy these objects.
4. Reduce memory usage: Reduce the size of each object as much as possible, which can reduce the amount of memory that needs to be allocated during program running, thereby reducing GC frequency. This can be achieved by using a structure instead of an array.

To sum up, Golang’s GC mechanism brings a lot of convenience, but it will also have some impact on the performance of the program. In order to improve the performance of the program, we need to take corresponding optimization measures based on the actual situation. Only by deeply understanding and proficiently using Golang's memory allocation mechanism can we better optimize the performance of Golang programs.

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