diff --git a/main.go b/main.go
index 3e2a40e..761d4d6 100644
--- a/main.go
+++ b/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"github.com/pkg/profile"
 	"io"
 	"log"
 	"monkey/compiler"
@@ -22,6 +23,9 @@ var (
 	compile     bool
 	version     bool
 	debug       bool
+
+	profileCPU bool
+	profileMem bool
 )
 
 func init() {
@@ -37,6 +41,9 @@ func init() {
 
 	flag.BoolVar(&interactive, "i", false, "enable interactive mode")
 	flag.StringVar(&engine, "e", "vm", "engine to use (eval or vm)")
+
+	flag.BoolVar(&profileCPU, "profile-cpu", false, "Enable CPU profiling.")
+	flag.BoolVar(&profileMem, "profile-mem", false, "Enable Memory profiling.")
 }
 
 // Indent indents a block of text with an indent string
@@ -70,6 +77,12 @@ func main() {
 
 	args := flag.Args()
 
+	if profileCPU {
+		defer profile.Start(profile.CPUProfile).Stop()
+	} else if profileMem {
+		defer profile.Start(profile.MemProfile).Stop()
+	}
+
 	if compile {
 		if len(args) < 1 {
 			log.Fatal("no source file given to compile")
diff --git a/vm/vm.go b/vm/vm.go
index 4a96ce2..c933514 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -105,10 +105,12 @@ type VM struct {
 	stack []object.Object
 	sp    int // Always points to the next value. Top of stack is stack[sp-1]
 
-	frames      []*Frame
-	framesIndex int
+	frames []*Frame
+	frame  *Frame // Current frame or nil
+	fp     int    // Always points to the current frame. Current frame is frames[fp-1]
 }
 
+// New constructs a new monkey-lang bytecode virtual machine
 func New(bytecode *compiler.Bytecode) *VM {
 	mainFn := &object.CompiledFunction{Instructions: bytecode.Instructions}
 	mainClosure := &object.Closure{Fn: mainFn}
@@ -126,8 +128,9 @@ func New(bytecode *compiler.Bytecode) *VM {
 		stack: make([]object.Object, StackSize),
 		sp:    0,
 
-		frames:      frames,
-		framesIndex: 1,
+		frames: frames,
+		frame:  mainFrame,
+		fp:     1,
 	}
 }
 
@@ -142,26 +145,25 @@ func NewWithState(bytecode *compiler.Bytecode, state *VMState) *VM {
 	return &VM{
 		state: state,
 
-		frames:      frames,
-		framesIndex: 1,
+		frames: frames,
+		frame:  mainFrame,
+		fp:     1,
 
 		stack: make([]object.Object, StackSize),
 		sp:    0,
 	}
 }
 
-func (vm *VM) currentFrame() *Frame {
-	return vm.frames[vm.framesIndex-1]
-}
-
 func (vm *VM) pushFrame(f *Frame) {
-	vm.frames[vm.framesIndex] = f
-	vm.framesIndex++
+	vm.frame = f
+	vm.frames[vm.fp] = f
+	vm.fp++
 }
 
 func (vm *VM) popFrame() *Frame {
-	vm.framesIndex--
-	return vm.frames[vm.framesIndex]
+	vm.fp--
+	vm.frame = vm.frames[vm.fp-1]
+	return vm.frames[vm.fp]
 }
 
 func (vm *VM) loadModule(name object.Object) error {
@@ -200,22 +202,22 @@ func (vm *VM) Run() error {
 			),
 			fmt.Sprintf(
 				"[ip=%02d fp=%02d, sp=%02d]",
-				ip, vm.framesIndex-1, vm.sp,
+				ip, vm.fp-1, vm.sp,
 			),
 		)
 	}
 
-	for vm.currentFrame().ip < len(vm.currentFrame().Instructions())-1 {
-		vm.currentFrame().ip++
+	for vm.frame.ip < len(vm.frame.Instructions())-1 {
+		vm.frame.ip++
 
-		ip = vm.currentFrame().ip
-		ins = vm.currentFrame().Instructions()
+		ip = vm.frame.ip
+		ins = vm.frame.Instructions()
 		op = code.Opcode(ins[ip])
 
 		switch op {
 		case code.OpConstant:
 			constIndex := code.ReadUint16(ins[ip+1:])
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			err := vm.push(vm.state.Constants[constIndex])
 			if err != nil {
@@ -271,15 +273,15 @@ func (vm *VM) Run() error {
 
 		case code.OpJump:
 			pos := int(code.ReadUint16(ins[ip+1:]))
-			vm.currentFrame().ip = pos - 1
+			vm.frame.ip = pos - 1
 
 		case code.OpJumpNotTruthy:
 			pos := int(code.ReadUint16(ins[ip+1:]))
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			condition := vm.pop()
 			if !isTruthy(condition) {
-				vm.currentFrame().ip = pos - 1
+				vm.frame.ip = pos - 1
 			}
 
 		case code.OpNull:
@@ -290,7 +292,7 @@ func (vm *VM) Run() error {
 
 		case code.OpSetGlobal:
 			globalIndex := code.ReadUint16(ins[ip+1:])
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			ref := vm.pop()
 			if immutable, ok := ref.(object.Immutable); ok {
@@ -306,7 +308,7 @@ func (vm *VM) Run() error {
 
 		case code.OpAssignGlobal:
 			globalIndex := code.ReadUint16(ins[ip+1:])
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 			vm.state.Globals[globalIndex] = vm.pop()
 
 			err := vm.push(Null)
@@ -316,10 +318,9 @@ func (vm *VM) Run() error {
 
 		case code.OpAssignLocal:
 			localIndex := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
+			vm.frame.ip += 1
 
-			frame := vm.currentFrame()
-			vm.stack[frame.basePointer+int(localIndex)] = vm.pop()
+			vm.stack[vm.frame.basePointer+int(localIndex)] = vm.pop()
 
 			err := vm.push(Null)
 			if err != nil {
@@ -328,7 +329,7 @@ func (vm *VM) Run() error {
 
 		case code.OpGetGlobal:
 			globalIndex := code.ReadUint16(ins[ip+1:])
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			err := vm.push(vm.state.Globals[globalIndex])
 			if err != nil {
@@ -337,7 +338,7 @@ func (vm *VM) Run() error {
 
 		case code.OpArray:
 			numElements := int(code.ReadUint16(ins[ip+1:]))
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			array := vm.buildArray(vm.sp-numElements, vm.sp)
 			vm.sp = vm.sp - numElements
@@ -349,7 +350,7 @@ func (vm *VM) Run() error {
 
 		case code.OpHash:
 			numElements := int(code.ReadUint16(ins[ip+1:]))
-			vm.currentFrame().ip += 2
+			vm.frame.ip += 2
 
 			hash, err := vm.buildHash(vm.sp-numElements, vm.sp)
 			if err != nil {
@@ -383,7 +384,7 @@ func (vm *VM) Run() error {
 
 		case code.OpCall:
 			numArgs := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
+			vm.frame.ip += 1
 
 			err := vm.executeCall(int(numArgs))
 			if err != nil {
@@ -403,15 +404,13 @@ func (vm *VM) Run() error {
 
 		case code.OpSetLocal:
 			localIndex := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
-
-			frame := vm.currentFrame()
+			vm.frame.ip += 1
 
 			ref := vm.pop()
 			if immutable, ok := ref.(object.Immutable); ok {
-				vm.stack[frame.basePointer+int(localIndex)] = immutable.Clone()
+				vm.stack[vm.frame.basePointer+int(localIndex)] = immutable.Clone()
 			} else {
-				vm.stack[frame.basePointer+int(localIndex)] = ref
+				vm.stack[vm.frame.basePointer+int(localIndex)] = ref
 			}
 
 			err := vm.push(Null)
@@ -421,18 +420,16 @@ func (vm *VM) Run() error {
 
 		case code.OpGetLocal:
 			localIndex := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
+			vm.frame.ip += 1
 
-			frame := vm.currentFrame()
-
-			err := vm.push(vm.stack[frame.basePointer+int(localIndex)])
+			err := vm.push(vm.stack[vm.frame.basePointer+int(localIndex)])
 			if err != nil {
 				return err
 			}
 
 		case code.OpGetBuiltin:
 			builtinIndex := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
+			vm.frame.ip += 1
 
 			builtin := builtins.BuiltinsIndex[builtinIndex]
 
@@ -444,7 +441,7 @@ func (vm *VM) Run() error {
 		case code.OpClosure:
 			constIndex := code.ReadUint16(ins[ip+1:])
 			numFree := code.ReadUint8(ins[ip+3:])
-			vm.currentFrame().ip += 3
+			vm.frame.ip += 3
 
 			err := vm.pushClosure(int(constIndex), int(numFree))
 			if err != nil {
@@ -453,16 +450,15 @@ func (vm *VM) Run() error {
 
 		case code.OpGetFree:
 			freeIndex := code.ReadUint8(ins[ip+1:])
-			vm.currentFrame().ip += 1
+			vm.frame.ip += 1
 
-			currentClosure := vm.currentFrame().cl
-			err := vm.push(currentClosure.Free[freeIndex])
+			err := vm.push(vm.frame.cl.Free[freeIndex])
 			if err != nil {
 				return err
 			}
 
 		case code.OpCurrentClosure:
-			currentClosure := vm.currentFrame().cl
+			currentClosure := vm.frame.cl
 			err := vm.push(currentClosure)
 			if err != nil {
 				return err
@@ -481,7 +477,7 @@ func (vm *VM) Run() error {
 		if vm.Debug {
 			log.Printf(
 				"%-25s [ip=%02d fp=%02d, sp=%02d]",
-				"", ip, vm.framesIndex-1, vm.sp,
+				"", ip, vm.fp-1, vm.sp,
 			)
 		}
 	}
@@ -844,14 +840,14 @@ func (vm *VM) callClosure(cl *object.Closure, numArgs int) error {
 	}
 
 	// Optimize tail calls and avoid a new frame
-	if cl.Fn == vm.currentFrame().cl.Fn {
-		nextOP := vm.currentFrame().NextOp()
+	if cl.Fn == vm.frame.cl.Fn {
+		nextOP := vm.frame.NextOp()
 		if nextOP == code.OpReturn {
 			for p := 0; p < numArgs; p++ {
-				vm.stack[vm.currentFrame().basePointer+p] = vm.stack[vm.sp-numArgs+p]
+				vm.stack[vm.frame.basePointer+p] = vm.stack[vm.sp-numArgs+p]
 			}
 			vm.sp -= numArgs + 1
-			vm.currentFrame().ip = -1 // reset IP to the beginning of the frame
+			vm.frame.ip = -1 // reset IP to the beginning of the frame
 			return nil
 		}
 	}