//   traceback may crash (and we want as much output as possible) or the stack
	//   may be changing.
	//
	// - Each physical frame can represent several logical frames, so we might
	//   have to pause in the middle of a physical frame and pick up in the middle
	//   of a physical frame.
	//
	// - The cgo symbolizer can expand a cgo PC to more than one logical frame,

	"internal/goarch"
	"internal/runtime/atomic"
	"runtime/internal/sys"
	"unsafe"
)

const (
	// minPhysPageSize is a lower-bound on the physical page size. The
	// true physical page size may be larger than this. In contrast,
	// sys.PhysPageSize is an upper-bound on the physical page size.
	minPhysPageSize = 4096

	// maxPhysPageSize is the maximum page size the runtime supports.
	maxPhysPageSize = 512 << 10

	// there's no point unless we're also returning the physical memory for these
	// metadata mappings back to the OS. That would be quite complex to do in general
	// as the heap is likely fragmented after a reduction in heap size.
	minHeapForMetadataHugePages = 1 << 30
)

// physPageSize is the size in bytes of the OS's physical pages.
// Mapping and unmapping operations must be done at multiples of

	blockProfile
	mutexProfile

	// size of bucket hash table
	buckHashSize = 179999

	// maxSkip is to account for deferred inline expansion
	// when using frame pointer unwinding. We record the stack
	// with "physical" frame pointers but handle skipping "logical"
	// frames at some point after collecting the stack. So
	// we need extra space in order to avoid getting fewer than the
	// desired maximum number of frames after expansion.