presto-main/src/main/java/io/prestosql/memory/NodeMemoryConfig.java/NodeMemoryConfig/setHeapHeadroom
class NodeMemoryConfig:    @Config("memory.heap-headroom-per-node")
    @ConfigDescription("The amount of heap memory to set aside as headroom/buffer (e.g., for untracked allocations)")
    public NodeMemoryConfig setHeapHeadroom(DataSize heapHeadroom)
    {
        this.heapHeadroom = heapHeadroom;
        return this;
    }