How Do I Calculate the Memory Footprint of a Go Map?

Computing the Memory Footprint of a Map in Go

Calculating the memory consumption of a map in Go can be challenging due to its dynamic data structure. However, there are methods to estimate the memory footprint using the underlying implementation details.

Map Structure

Internally, a Go map is represented as a header (hmap) and a series of buckets (bmap). The header stores information such as the number of elements, bucket count, and hash seed. Each bucket contains the hash value, key, and value for a specific element.

Calculating Memory Footprint

To estimate the memory footprint of a map, the following formula can be used:

unsafe.Sizeof(hmap) + (len(theMap) * 8) + (len(theMap) * 8 * unsafe.Sizeof(x)) + (len(theMap) * 8 * unsafe.Sizeof(y))

• unsafe.Sizeof(hmap): Size of the map header
• len(theMap) * 8: Size of the keys and values (assuming both are 64-bit)
• len(theMap) * 8 * unsafe.Sizeof(x): Size of the keys
• len(theMap) * 8 * unsafe.Sizeof(y): Size of the values

Example Calculation

For a map with 100 elements, a key type of string, and a value type of int, the estimated memory footprint would be:

unsafe.Sizeof(hmap) + (100 * 8) + (100 * 8 * unsafe.Sizeof(string)) + (100 * 8 * unsafe.Sizeof(int))

Note:

The calculation assumes that the map is not dense (i.e., there are no empty buckets). This assumption should hold true for most practical scenarios.

The above is the detailed content of How Do I Calculate the Memory Footprint of a Go Map?. For more information, please follow other related articles on the PHP Chinese website!