Why Does Go's Memory Usage for Short and Long Strings Appear Identical?

String Memory Usage in Golang

Optimizing code often involves considering memory usage. Let's examine the example of a map[string]string where the values are either "A" or "B." It would seem logical to use a map[string]bool instead, as it would require less memory.

However, testing revealed a surprising result. The memory usage of a string with a single character ("a") and a string with a very long character sequence ("a2") were the same.

To understand this behavior, we need to consider how Go handles memory for strings and maps.

Understanding Go's Memory Handling

• Maps: In Go, maps are implemented using pointers. Therefore, unsafe.Sizeof(somemap) will report the size of the pointer to the map, not the size of the actual data it contains.
• Strings: Strings in Go are represented by a struct containing a pointer to the data and its length. Thus, unsafe.Sizeof(somestring) reports the size of this struct, which is independent of the length of the string.

Calculating Actual Memory Usage

To determine the actual memory requirement of a map or string, we need to consider the data it holds.

• Maps: For maps, the memory requirement is not only the size of the pointer but also the memory allocated for the key-value pairs. To get this deep size, you can refer to other resources such as [this StackOverflow question](https://stackoverflow.com/questions/33159892/how-much-memory-do-golang-maps-reserve).
• Strings: Go stores string values in memory as UTF-8 encoded byte sequences. The memory requirement is the length of the string plus the size of the header struct:

stringSize := len(str) + int(unsafe.Sizeof(str))

Additional Considerations

• String Slicing: When you slice a string, the backing array for the original string will still be retained in memory, even if it is no longer referenced. This can impact the memory usage of smaller string slices.

In summary, while unsafe.Sizeof() can provide insights into memory usage, it does not provide a complete picture. For accurate memory calculations, consider the actual data structures and their content.

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