A MemStats records statistics about the memory allocator.


type MemStats struct {
	// General statistics.
	Alloc      uint64 // bytes allocated and not yet freed
	TotalAlloc uint64 // bytes allocated (even if freed)
	Sys        uint64 // bytes obtained from system (sum of XxxSys below)
	Lookups    uint64 // number of pointer lookups
	Mallocs    uint64 // number of mallocs
	Frees      uint64 // number of frees

	// Main allocation heap statistics.
	HeapAlloc    uint64 // bytes allocated and not yet freed (same as Alloc above)
	HeapSys      uint64 // bytes obtained from system
	HeapIdle     uint64 // bytes in idle spans
	HeapInuse    uint64 // bytes in non-idle span
	HeapReleased uint64 // bytes released to the OS
	HeapObjects  uint64 // total number of allocated objects

	// Low-level fixed-size structure allocator statistics.
	//	Inuse is bytes used now.
	//	Sys is bytes obtained from system.
	StackInuse  uint64 // bytes used by stack allocator
	StackSys    uint64
	MSpanInuse  uint64 // mspan structures
	MSpanSys    uint64
	MCacheInuse uint64 // mcache structures
	MCacheSys   uint64
	BuckHashSys uint64 // profiling bucket hash table
	GCSys       uint64 // GC metadata
	OtherSys    uint64 // other system allocations

	// Garbage collector statistics.
	NextGC        uint64 // next collection will happen when HeapAlloc ≥ this amount
	LastGC        uint64 // end time of last collection (nanoseconds since 1970)
	PauseTotalNs  uint64
	PauseNs       [256]uint64 // circular buffer of recent GC pause durations, most recent at [(NumGC+255)%256]
	PauseEnd      [256]uint64 // circular buffer of recent GC pause end times
	NumGC         uint32
	GCCPUFraction float64 // fraction of CPU time used by GC
	EnableGC      bool
	DebugGC       bool

	// Per-size allocation statistics.
	// 61 is NumSizeClasses in the C code.
	BySize [61]struct {
		Size    uint32
		Mallocs uint64
		Frees   uint64