diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 2da13f2073b..31335dae805 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -711,7 +711,7 @@ func mallocgc(size uintptr, typ *_type, flags uint32) unsafe.Pointer {
 			s = largeAlloc(size, flags)
 		})
 		s.freeindex = 1
-		x = unsafe.Pointer(uintptr(s.start << pageShift))
+		x = unsafe.Pointer(s.base())
 		size = s.elemsize
 	}
 
@@ -833,7 +833,7 @@ func largeAlloc(size uintptr, flag uint32) *mspan {
 	if s == nil {
 		throw("out of memory")
 	}
-	s.limit = uintptr(s.start)<<_PageShift + size
+	s.limit = s.base() + size
 	heapBitsForSpan(s.base()).initSpan(s)
 	return s
 }
diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index ea398904e34..b342de600e2 100644
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -457,7 +457,7 @@ func heapBitsForObject(p, refBase, refOff uintptr) (base uintptr, hbits heapBits
 			} else {
 				print(" to unused region of span")
 			}
-			print("idx=", hex(idx), " span.start=", hex(s.start<<_PageShift), " span.limit=", hex(s.limit), " span.state=", s.state, "\n")
+			print("idx=", hex(idx), " span.base()=", hex(s.base()), " span.limit=", hex(s.limit), " span.state=", s.state, "\n")
 			if refBase != 0 {
 				print("runtime: found in object at *(", hex(refBase), "+", hex(refOff), ")\n")
 				gcDumpObject("object", refBase, refOff)
diff --git a/src/runtime/mcentral.go b/src/runtime/mcentral.go
index d5f05ae639f..bbbfb18fbf8 100644
--- a/src/runtime/mcentral.go
+++ b/src/runtime/mcentral.go
@@ -212,7 +212,7 @@ func (c *mcentral) grow() *mspan {
 		return nil
 	}
 
-	p := uintptr(s.start << _PageShift)
+	p := s.base()
 	s.limit = p + size*n
 
 	heapBitsForSpan(s.base()).initSpan(s)
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index fe8a56460ba..47456857e9c 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -287,7 +287,7 @@ func markrootSpans(gcw *gcWork, shard int) {
 			// retain everything it points to.
 			spf := (*specialfinalizer)(unsafe.Pointer(sp))
 			// A finalizer can be set for an inner byte of an object, find object beginning.
-			p := uintptr(s.start<<_PageShift) + uintptr(spf.special.offset)/s.elemsize*s.elemsize
+			p := s.base() + uintptr(spf.special.offset)/s.elemsize*s.elemsize
 
 			// Mark everything that can be reached from
 			// the object (but *not* the object itself or
diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go
index 1a6be6634dd..9316cc6f499 100644
--- a/src/runtime/mgcsweep.go
+++ b/src/runtime/mgcsweep.go
@@ -211,13 +211,13 @@ func (s *mspan) sweep(preserve bool) bool {
 	special := *specialp
 	for special != nil {
 		// A finalizer can be set for an inner byte of an object, find object beginning.
-		p := uintptr(s.start<<_PageShift) + uintptr(special.offset)/size*size
+		p := s.base() + uintptr(special.offset)/size*size
 		mbits := s.markBitsForAddr(p)
 		if !mbits.isMarked() {
 			// This object is not marked and has at least one special record.
 			// Pass 1: see if it has at least one finalizer.
 			hasFin := false
-			endOffset := p - uintptr(s.start<<_PageShift) + size
+			endOffset := p - s.base() + size
 			for tmp := special; tmp != nil && uintptr(tmp.offset) < endOffset; tmp = tmp.next {
 				if tmp.kind == _KindSpecialFinalizer {
 					// Stop freeing of object if it has a finalizer.
@@ -230,7 +230,7 @@ func (s *mspan) sweep(preserve bool) bool {
 			for special != nil && uintptr(special.offset) < endOffset {
 				// Find the exact byte for which the special was setup
 				// (as opposed to object beginning).
-				p := uintptr(s.start<<_PageShift) + uintptr(special.offset)
+				p := s.base() + uintptr(special.offset)
 				if special.kind == _KindSpecialFinalizer || !hasFin {
 					// Splice out special record.
 					y := special
@@ -311,7 +311,7 @@ func (s *mspan) sweep(preserve bool) bool {
 		// implement and then call some kind of MHeap_DeleteSpan.
 		if debug.efence > 0 {
 			s.limit = 0 // prevent mlookup from finding this span
-			sysFault(unsafe.Pointer(uintptr(s.start<<_PageShift)), size)
+			sysFault(unsafe.Pointer(s.base()), size)
 		} else {
 			mheap_.freeSpan(s, 1)
 		}
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index b0b3bbd9576..9f07dfbb995 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -116,7 +116,8 @@ type mspan struct {
 	next *mspan     // next span in list, or nil if none
 	prev **mspan    // previous span's next field, or list head's first field if none
 	list *mSpanList // For debugging. TODO: Remove.
-
+	//TODO:(rlh) Eliminate start field and use startAddr >> PageShift instead.
+	startAddr     uintptr   // uintptr(s.start << _PageShift) aka s.base()
 	start         pageID    // starting page number
 	npages        uintptr   // number of pages in span
 	stackfreelist gclinkptr // list of free stacks, avoids overloading freelist
@@ -184,7 +185,7 @@ type mspan struct {
 }
 
 func (s *mspan) base() uintptr {
-	return uintptr(s.start << _PageShift)
+	return s.startAddr
 }
 
 func (s *mspan) layout() (size, n, total uintptr) {
@@ -300,7 +301,7 @@ func mlookup(v uintptr, base *uintptr, size *uintptr, sp **mspan) int32 {
 		return 0
 	}
 
-	p := uintptr(s.start) << _PageShift
+	p := s.base()
 	if s.sizeclass == 0 {
 		// Large object.
 		if base != nil {
@@ -542,7 +543,7 @@ func (h *mheap) alloc(npage uintptr, sizeclass int32, large bool, needzero bool)
 
 	if s != nil {
 		if needzero && s.needzero != 0 {
-			memclr(unsafe.Pointer(s.start<<_PageShift), s.npages<<_PageShift)
+			memclr(unsafe.Pointer(s.base()), s.npages<<_PageShift)
 		}
 		s.needzero = 0
 	}
@@ -610,7 +611,7 @@ HaveSpan:
 		throw("still in list")
 	}
 	if s.npreleased > 0 {
-		sysUsed(unsafe.Pointer(s.start<<_PageShift), s.npages<<_PageShift)
+		sysUsed(unsafe.Pointer(s.base()), s.npages<<_PageShift)
 		memstats.heap_released -= uint64(s.npreleased << _PageShift)
 		s.npreleased = 0
 	}
@@ -826,6 +827,7 @@ func (h *mheap) freeSpanLocked(s *mspan, acctinuse, acctidle bool, unusedsince i
 		t := h_spans[p-1]
 		if t != nil && t.state == _MSpanFree {
 			s.start = t.start
+			s.startAddr = uintptr(s.start << _PageShift)
 			s.npages += t.npages
 			s.npreleased = t.npreleased // absorb released pages
 			s.needzero |= t.needzero
@@ -925,6 +927,7 @@ func (span *mspan) init(start pageID, npages uintptr) {
 	span.prev = nil
 	span.list = nil
 	span.start = start
+	span.startAddr = uintptr(start << _PageShift)
 	span.npages = npages
 	span.allocCount = 0
 	span.sizeclass = 0