How does the garbage collection mechanism work in Go language?

The Go language is an open source statically typed programming language developed by Google and debuted in 2009. It is characterized by simple syntax, high performance, convenient concurrent programming, etc., so it is loved by more and more programmers.

In the Go language, there is generally no need to manually manage memory because it provides a garbage collection mechanism that can automatically manage memory. So, how does the garbage collection mechanism in Go language work? This article will introduce it to you.

Garbage collection mechanism in Go language

The garbage collection mechanism in Go language uses the mark-sweep algorithm. This is a common garbage collection algorithm and one of the earliest used garbage collection algorithms. It traverses reachable objects, marks all living objects in the heap, and then clears unmarked objects. The main advantages of this algorithm are that it can clear discontinuous memory and can handle circular references, but its disadvantage is that it will introduce significant pause time and space fragmentation.

The garbage collection mechanism in the Go language is performed at runtime. It continuously monitors the objects in the heap while the program is running and performs garbage collection regularly. While garbage collection is in progress, the program suspends the current thread until the collection is complete. Although this process will have a certain impact on the running of the program, it can better manage memory and reduce the risk of memory leaks.

At the same time, the garbage collection mechanism of Go language also uses three-color marking. This method will mark all objects in the heap as white, which means they have not been scanned; gray, which means they have been scanned but the traversal has not been completed; black, which means they have been scanned and the traversal has been completed. The garbage collector will scan from the root object, marking reachable objects in black and unreachable objects in white. During cleaning, only black objects will be retained and white objects will be released. In addition, when the number of black objects exceeds a certain proportion, the garbage collector will re-mark and clear to reduce memory fragmentation.

Optimization methods of garbage collector

As a high-performance programming language, the garbage collector of Go language is also constantly being optimized. These optimization methods include:

1. Concurrency mark

Before Go language version 1.5, garbage collection required pausing the entire program, which would have a great performance impact. Starting from Go language version 1.5, the garbage collector has introduced a concurrent marking mechanism, which can perform garbage collection while the program is running, reducing the impact of garbage collection on the program.

2. Compressed memory

Garbage collection will cause memory fragmentation and cause problems with heap memory allocation. The garbage collector of the Go language uses memory compression technology to solve the problem of memory fragmentation by moving objects in memory together.

3. Small object optimization

The garbage collector uses small object optimization technology to avoid garbage collection of small objects and reduce the cost of memory recycling.

Summary

Through the above introduction, we can understand how the garbage collection mechanism in the Go language works and its main optimization methods. The garbage collector reduces the memory management of programmers to a great extent, allowing programmers to focus more on the implementation of business logic. At the same time, the garbage collection mechanism of the Go language can also be configured by environment variables to meet different application scenarios.

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