diff --git a/src/runtime/mcentral.go b/src/runtime/mcentral.go
index 8f9c529539..5302dd8e3d 100644
--- a/src/runtime/mcentral.go
+++ b/src/runtime/mcentral.go
@@ -126,9 +126,6 @@ havespan:
 	// mcache. If it gets uncached, we'll adjust this.
 	atomic.Xadd64(&c.nmalloc, int64(n))
 	usedBytes := uintptr(s.allocCount) * s.elemsize
-	if usedBytes > 0 {
-		reimburseSweepCredit(usedBytes)
-	}
 	atomic.Xadd64(&memstats.heap_live, int64(spanBytes)-int64(usedBytes))
 	if trace.enabled {
 		// heap_live changed.
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 88722699a6..8cba9f72bb 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -839,7 +839,8 @@ func gcSetTriggerRatio(triggerRatio float64) {
 		// pages by the time the allocated heap reaches the GC
 		// trigger. Compute the ratio of in-use pages to sweep
 		// per byte allocated.
-		heapDistance := int64(trigger) - int64(atomic.Load64(&memstats.heap_live))
+		heapLiveBasis := atomic.Load64(&memstats.heap_live)
+		heapDistance := int64(trigger) - int64(heapLiveBasis)
 		// Add a little margin so rounding errors and
 		// concurrent sweep are less likely to leave pages
 		// unswept when GC starts.
@@ -850,7 +851,7 @@ func gcSetTriggerRatio(triggerRatio float64) {
 		}
 		mheap_.sweepPagesPerByte = float64(mheap_.pagesInUse) / float64(heapDistance)
 		mheap_.pagesSwept = 0
-		mheap_.spanBytesAlloc = 0
+		mheap_.sweepHeapLiveBasis = heapLiveBasis
 	}
 }
 
diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go
index dd0682594a..8915b398cd 100644
--- a/src/runtime/mgcsweep.go
+++ b/src/runtime/mgcsweep.go
@@ -123,7 +123,7 @@ func sweepone() uintptr {
 	// last one print trace information.
 	if atomic.Xadd(&mheap_.sweepers, -1) == 0 && atomic.Load(&mheap_.sweepdone) != 0 {
 		if debug.gcpacertrace > 0 {
-			print("pacer: sweep done at heap size ", memstats.heap_live>>20, "MB; allocated ", mheap_.spanBytesAlloc>>20, "MB of spans; swept ", mheap_.pagesSwept, " pages at ", sweepRatio, " pages/byte\n")
+			print("pacer: sweep done at heap size ", memstats.heap_live>>20, "MB; allocated ", (memstats.heap_live-mheap_.sweepHeapLiveBasis)>>20, "MB during sweep; swept ", mheap_.pagesSwept, " pages at ", sweepRatio, " pages/byte\n")
 		}
 	}
 	_g_.m.locks--
@@ -379,8 +379,7 @@ func (s *mspan) sweep(preserve bool) bool {
 //
 // deductSweepCredit makes a worst-case assumption that all spanBytes
 // bytes of the ultimately allocated span will be available for object
-// allocation. The caller should call reimburseSweepCredit if that
-// turns out not to be the case once the span is allocated.
+// allocation.
 //
 // deductSweepCredit is the core of the "proportional sweep" system.
 // It uses statistics gathered by the garbage collector to perform
@@ -398,12 +397,10 @@ func deductSweepCredit(spanBytes uintptr, callerSweepPages uintptr) {
 		traceGCSweepStart()
 	}
 
-	// Account for this span allocation.
-	spanBytesAlloc := atomic.Xadd64(&mheap_.spanBytesAlloc, int64(spanBytes))
-
 	// Fix debt if necessary.
-	pagesOwed := int64(mheap_.sweepPagesPerByte * float64(spanBytesAlloc))
-	for pagesOwed-int64(atomic.Load64(&mheap_.pagesSwept)) > int64(callerSweepPages) {
+	newHeapLive := uintptr(atomic.Load64(&memstats.heap_live)-mheap_.sweepHeapLiveBasis) + spanBytes
+	pagesTarget := int64(mheap_.sweepPagesPerByte*float64(newHeapLive)) - int64(callerSweepPages)
+	for pagesTarget > int64(atomic.Load64(&mheap_.pagesSwept)) {
 		if gosweepone() == ^uintptr(0) {
 			mheap_.sweepPagesPerByte = 0
 			break
@@ -414,19 +411,3 @@ func deductSweepCredit(spanBytes uintptr, callerSweepPages uintptr) {
 		traceGCSweepDone()
 	}
 }
-
-// reimburseSweepCredit records that unusableBytes bytes of a
-// just-allocated span are not available for object allocation. This
-// offsets the worst-case charge performed by deductSweepCredit.
-func reimburseSweepCredit(unusableBytes uintptr) {
-	if mheap_.sweepPagesPerByte == 0 {
-		// Nobody cares about the credit. Avoid the atomic.
-		return
-	}
-	nval := atomic.Xadd64(&mheap_.spanBytesAlloc, -int64(unusableBytes))
-	if int64(nval) < 0 {
-		// Debugging for #18043.
-		print("runtime: bad spanBytesAlloc=", nval, " (was ", nval+uint64(unusableBytes), ") unusableBytes=", unusableBytes, " sweepPagesPerByte=", mheap_.sweepPagesPerByte, "\n")
-		throw("spanBytesAlloc underflow")
-	}
-}
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index e1b3b184e8..643fc7c502 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -75,10 +75,10 @@ type mheap struct {
 	_ uint32 // align uint64 fields on 32-bit for atomics
 
 	// Proportional sweep
-	pagesInUse        uint64  // pages of spans in stats _MSpanInUse; R/W with mheap.lock
-	spanBytesAlloc    uint64  // bytes of spans allocated this cycle; updated atomically
-	pagesSwept        uint64  // pages swept this cycle; updated atomically
-	sweepPagesPerByte float64 // proportional sweep ratio; written with lock, read without
+	pagesInUse         uint64  // pages of spans in stats _MSpanInUse; R/W with mheap.lock
+	pagesSwept         uint64  // pages swept this cycle; updated atomically
+	sweepHeapLiveBasis uint64  // value of heap_live to use as the origin of sweep ratio; written with lock, read without
+	sweepPagesPerByte  float64 // proportional sweep ratio; written with lock, read without
 	// TODO(austin): pagesInUse should be a uintptr, but the 386
 	// compiler can't 8-byte align fields.