runtime: fix memstats

Newly allocated memory is subtracted from inuse, while it was never added to inuse.
Span leftovers are subtracted from both inuse and idle,
while they were never added.
Fixes #8544.
Fixes #8430.

LGTM=khr, cookieo9
R=golang-codereviews, khr, cookieo9
CC=golang-codereviews, rlh, rsc
https://golang.org/cl/130200044

1 files changed, 19 insertions, 3 deletions

diff --git a/src/pkg/runtime/malloc_test.go b/src/pkg/runtime/malloc_test.go
index 252760a07e..211d78dc8a 100644
--- a/src/pkg/runtime/malloc_test.go
+++ b/src/pkg/runtime/malloc_test.go
@@ -16,10 +16,26 @@ func TestMemStats(t *testing.T) {
 	// Test that MemStats has sane values.
 	st := new(MemStats)
 	ReadMemStats(st)
-	if st.HeapSys == 0 || st.StackSys == 0 || st.MSpanSys == 0 || st.MCacheSys == 0 ||
-		st.BuckHashSys == 0 || st.GCSys == 0 || st.OtherSys == 0 {
-		t.Fatalf("Zero sys value: %+v", *st)
+
+	// Everything except HeapReleased, because it indeed can be 0.
+	if st.Alloc == 0 || st.TotalAlloc == 0 || st.Sys == 0 || st.Lookups == 0 ||
+		st.Mallocs == 0 || st.Frees == 0 || st.HeapAlloc == 0 || st.HeapSys == 0 ||
+		st.HeapIdle == 0 || st.HeapInuse == 0 || st.HeapObjects == 0 || st.StackInuse == 0 ||
+		st.StackSys == 0 || st.MSpanInuse == 0 || st.MSpanSys == 0 || st.MCacheInuse == 0 ||
+		st.MCacheSys == 0 || st.BuckHashSys == 0 || st.GCSys == 0 || st.OtherSys == 0 ||
+		st.NextGC == 0 || st.NumGC == 0 {
+		t.Fatalf("Zero value: %+v", *st)
+	}
+
+	if st.Alloc > 1e10 || st.TotalAlloc > 1e11 || st.Sys > 1e10 || st.Lookups > 1e10 ||
+		st.Mallocs > 1e10 || st.Frees > 1e10 || st.HeapAlloc > 1e10 || st.HeapSys > 1e10 ||
+		st.HeapIdle > 1e10 || st.HeapInuse > 1e10 || st.HeapObjects > 1e10 || st.StackInuse > 1e10 ||
+		st.StackSys > 1e10 || st.MSpanInuse > 1e10 || st.MSpanSys > 1e10 || st.MCacheInuse > 1e10 ||
+		st.MCacheSys > 1e10 || st.BuckHashSys > 1e10 || st.GCSys > 1e10 || st.OtherSys > 1e10 ||
+		st.NextGC > 1e10 || st.NumGC > 1e9 {
+		t.Fatalf("Insanely high value (overflow?): %+v", *st)
 	}
+
 	if st.Sys != st.HeapSys+st.StackSys+st.MSpanSys+st.MCacheSys+
 		st.BuckHashSys+st.GCSys+st.OtherSys {
 		t.Fatalf("Bad sys value: %+v", *st)