image-20220512210618415

缘起

来自于一段prometheus代码

type stripeLock struct { 
	sync.RWMutex
	// Padding to avoid multiple locks being on the same cache line.
	_ [40]byte
}

简单地讲就是因为CPU读取数据的缓存机制问题，可能导致性能上的不同差异。参考资料见后文。

常见类型的内存占用大小（Go101）：

Kinds of Types Value Size Required by Go Specification
bool 1 byte not specified
int8, uint8 (byte) 1 byte 1 byte
int16, uint16 2 bytes 2 bytes
int32 (rune), uint32, float32 4 bytes 4 bytes
int64, uint64, float64, complex64 8 bytes 8 bytes
complex128 16 bytes 16 bytes
int, uint 1 word architecture dependent, 4 bytes on 32-bit architectures and 8 bytes on 64-bit architectures
uintptr 1 word large enough to store the uninterpreted bits of a pointer value
string 2 words not specified
pointer (safe or unsafe) 1 word not specified
slice 3 words not specified
map 1 word not specified
channel 1 word not specified
function 1 word not specified
interface 2 words not specified
struct (the sum of sizes of all fields) + (the number of padding bytes) the size of a struct type is zero if it contains no fields that have a size greater than zero
array (element value size) * (array length) the size of an array type is zero if its element type has zero size

参考