// which prevents us from allocating more stack.
//
//go:nosplit
func sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
	sysStat.add(int64(n))
	gcController.mappedReady.Add(int64(n))
	return sysAllocOS(n)
}

// sysUnused transitions a memory region from Ready to Prepared. It notifies the
// operating system that the physical pages backing this memory region are no

func (s *scavengeIndex) sysInit(test bool, sysStat *sysMemStat) (mappedReady uintptr) {
	if test {
		// Set up the scavenge index via sysAlloc so the test can free it later.
		scavIndexSize := uintptr(len(scavengeIndexArray)) * unsafe.Sizeof(atomicScavChunkData{})
		s.chunks = ((*[(1 << heapAddrBits) / pallocChunkBytes]atomicScavChunkData)(sysAlloc(scavIndexSize, sysStat)))[:]
		mappedReady = scavIndexSize
	} else {
		// Set up the scavenge index.