[dev.garbage] runtime: replace ref with allocCount

This is a renaming of the field ref to the
more appropriate allocCount. The field
holds the number of objects in the span
that are currently allocated. Some throws
strings were adjusted to more accurately
convey the meaning of allocCount.

Change-Id: I10daf44e3e9cc24a10912638c7de3c1984ef8efe
Reviewed-on: https://go-review.googlesource.com/19518
Reviewed-by: Austin Clements <austin@google.com>

src/runtime/malloc.go

@@ -509,8 +509,8 @@ func (c *mcache) nextFree(sizeclass int8) (v gclinkptr, shouldhelpgc bool) {
 
 	if freeIndex == s.nelems {
 		// The span is full.
-		if uintptr(s.ref) != s.nelems {
-			throw("s.ref != s.nelems && freeIndex == s.nelems")
+		if uintptr(s.allocCount) != s.nelems {
+			throw("s.allocCount != s.nelems && freeIndex == s.nelems")
 		}
 		systemstack(func() {
 			c.refill(int32(sizeclass))
@@ -526,9 +526,9 @@ func (c *mcache) nextFree(sizeclass int8) (v gclinkptr, shouldhelpgc bool) {
 	v = gclinkptr(freeIndex*s.elemsize + s.base())
 	// Advance the freeIndex.
 	s.freeindex = freeIndex + 1
-	s.ref++
-	if uintptr(s.ref) > s.nelems {
-		throw("s.ref > s.nelems")
+	s.allocCount++
+	if uintptr(s.allocCount) > s.nelems {
+		throw("s.allocCount > s.nelems")
 	}
 	return
 }

src/runtime/mcache.go

@@ -109,7 +109,7 @@ func (c *mcache) refill(sizeclass int32) *mspan {
 	// Return the current cached span to the central lists.
 	s := c.alloc[sizeclass]
 
-	if uintptr(s.ref) != s.nelems {
+	if uintptr(s.allocCount) != s.nelems {
 		throw("refill of span with free space remaining")
 	}
 
@@ -123,7 +123,7 @@ func (c *mcache) refill(sizeclass int32) *mspan {
 		throw("out of memory")
 	}
 
-	if uintptr(s.ref) == s.nelems {
+	if uintptr(s.allocCount) == s.nelems {
 		throw("span has no free space")
 	}
 

src/runtime/mcentral.go

@@ -100,11 +100,11 @@ retry:
 	// c is unlocked.
 havespan:
 	cap := int32((s.npages << _PageShift) / s.elemsize)
-	n := cap - int32(s.ref)
+	n := cap - int32(s.allocCount)
 	if n == 0 {
-		throw("empty span")
+		throw("span has no free objects")
 	}
-	usedBytes := uintptr(s.ref) * s.elemsize
+	usedBytes := uintptr(s.allocCount) * s.elemsize
 	if usedBytes > 0 {
 		reimburseSweepCredit(usedBytes)
 	}
@@ -127,12 +127,12 @@ func (c *mcentral) uncacheSpan(s *mspan) {
 
 	s.incache = false
 
-	if s.ref == 0 {
-		throw("uncaching full span")
+	if s.allocCount == 0 {
+		throw("uncaching span but s.allocCount == 0")
 	}
 
 	cap := int32((s.npages << _PageShift) / s.elemsize)
-	n := cap - int32(s.ref)
+	n := cap - int32(s.allocCount)
 	if n > 0 {
 		c.empty.remove(s)
 		c.nonempty.insert(s)
@@ -154,7 +154,7 @@ func (c *mcentral) freeSpan(s *mspan, n int32, start gclinkptr, end gclinkptr, p
 		throw("freeSpan given cached span")
 	}
 
-	s.ref -= uint16(n)
+	s.allocCount -= uint16(n)
 
 	if preserve {
 		// preserve is set only when called from MCentral_CacheSpan above,
@@ -180,7 +180,7 @@ func (c *mcentral) freeSpan(s *mspan, n int32, start gclinkptr, end gclinkptr, p
 	// lock of c above.)
 	atomic.Store(&s.sweepgen, mheap_.sweepgen)
 
-	if s.ref != 0 {
+	if s.allocCount != 0 {
 		unlock(&c.lock)
 		return false
 	}

src/runtime/mheap.go

@@ -159,7 +159,7 @@ type mspan struct {
 
 	sweepgen    uint32
 	divMul      uint32   // for divide by elemsize - divMagic.mul
-	ref         uint16   // capacity - number of objects in freelist
+	allocCount  uint16   // capacity - number of objects in freelist
 	sizeclass   uint8    // size class
 	incache     bool     // being used by an mcache
 	state       uint8    // mspaninuse etc
@@ -471,7 +471,7 @@ func (h *mheap) alloc_m(npage uintptr, sizeclass int32, large bool) *mspan {
 		// able to map interior pointer to containing span.
 		atomic.Store(&s.sweepgen, h.sweepgen)
 		s.state = _MSpanInUse
-		s.ref = 0
+		s.allocCount = 0
 		s.sizeclass = uint8(sizeclass)
 		if sizeclass == 0 {
 			s.elemsize = s.npages << _PageShift
@@ -551,7 +551,7 @@ func (h *mheap) allocStack(npage uintptr) *mspan {
 	if s != nil {
 		s.state = _MSpanStack
 		s.stackfreelist = 0
-		s.ref = 0
+		s.allocCount = 0
 		memstats.stacks_inuse += uint64(s.npages << _PageShift)
 	}
 
@@ -773,12 +773,12 @@ func (h *mheap) freeStack(s *mspan) {
 func (h *mheap) freeSpanLocked(s *mspan, acctinuse, acctidle bool, unusedsince int64) {
 	switch s.state {
 	case _MSpanStack:
-		if s.ref != 0 {
+		if s.allocCount != 0 {
 			throw("MHeap_FreeSpanLocked - invalid stack free")
 		}
 	case _MSpanInUse:
-		if s.ref != 0 || s.sweepgen != h.sweepgen {
-			print("MHeap_FreeSpanLocked - span ", s, " ptr ", hex(s.start<<_PageShift), " ref ", s.ref, " sweepgen ", s.sweepgen, "/", h.sweepgen, "\n")
+		if s.allocCount != 0 || s.sweepgen != h.sweepgen {
+			print("MHeap_FreeSpanLocked - span ", s, " ptr ", hex(s.start<<_PageShift), " allocCount ", s.allocCount, " sweepgen ", s.sweepgen, "/", h.sweepgen, "\n")
 			throw("MHeap_FreeSpanLocked - invalid free")
 		}
 		h.pagesInUse -= uint64(s.npages)
@@ -912,7 +912,7 @@ func (span *mspan) init(start pageID, npages uintptr) {
 	span.list = nil
 	span.start = start
 	span.npages = npages
-	span.ref = 0
+	span.allocCount = 0
 	span.sizeclass = 0
 	span.incache = false
 	span.elemsize = 0

src/runtime/mstats.go

@@ -295,9 +295,9 @@ func updatememstats(stats *gcstats) {
 			memstats.nmalloc++
 			memstats.alloc += uint64(s.elemsize)
 		} else {
-			memstats.nmalloc += uint64(s.ref)
-			memstats.by_size[s.sizeclass].nmalloc += uint64(s.ref)
-			memstats.alloc += uint64(s.ref) * uint64(s.elemsize)
+			memstats.nmalloc += uint64(s.allocCount)
+			memstats.by_size[s.sizeclass].nmalloc += uint64(s.allocCount)
+			memstats.alloc += uint64(s.allocCount) * uint64(s.elemsize)
 		}
 	}
 	unlock(&mheap_.lock)

src/runtime/stack.go

@@ -191,8 +191,8 @@ func stackpoolalloc(order uint8) gclinkptr {
 		if s == nil {
 			throw("out of memory")
 		}
-		if s.ref != 0 {
-			throw("bad ref")
+		if s.allocCount != 0 {
+			throw("bad allocCount")
 		}
 		if s.stackfreelist.ptr() != nil {
 			throw("bad stackfreelist")
@@ -209,7 +209,7 @@ func stackpoolalloc(order uint8) gclinkptr {
 		throw("span has no free stacks")
 	}
 	s.stackfreelist = x.ptr().next
-	s.ref++
+	s.allocCount++
 	if s.stackfreelist.ptr() == nil {
 		// all stacks in s are allocated.
 		list.remove(s)
@@ -229,8 +229,8 @@ func stackpoolfree(x gclinkptr, order uint8) {
 	}
 	x.ptr().next = s.stackfreelist
 	s.stackfreelist = x
-	s.ref--
-	if gcphase == _GCoff && s.ref == 0 {
+	s.allocCount--
+	if gcphase == _GCoff && s.allocCount == 0 {
 		// Span is completely free. Return it to the heap
 		// immediately if we're sweeping.
 		//
@@ -1135,7 +1135,7 @@ func freeStackSpans() {
 		list := &stackpool[order]
 		for s := list.first; s != nil; {
 			next := s.next
-			if s.ref == 0 {
+			if s.allocCount == 0 {
 				list.remove(s)
 				s.stackfreelist = 0
 				mheap_.freeStack(s)