In TestReadLargeMemCheck, allow for more memory use on 64 bit

platform.

fuse/loopback_test.go

@@ -14,6 +14,7 @@ import (
 	"syscall"
 	"testing"
 	"time"
+	"unsafe"
 )
 
 var _ = strings.Join
@@ -601,6 +602,9 @@ func TestReadLargeMemCheck(t *testing.T) {
 	delta = (delta - 40000) / N
 
 	limit := 5000
+	if unsafe.Sizeof(uintptr(0)) == 8 {
+		limit = 10000
+	}
 	if delta > limit {
 		t.Errorf("bytes per loop: %d, limit %d", delta, limit)
 	}