diff -r 4cbfa5077d68 -r 623722a6aeb9 src/hotspot/share/gc/shenandoah/shenandoahHeapRegionCounters.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegionCounters.cpp	Mon Nov 25 12:32:40 2019 +0100
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegionCounters.cpp	Mon Nov 25 12:33:15 2019 +0100
@@ -76,7 +76,7 @@
     jlong current = os::javaTimeMillis();
     jlong last = _last_sample_millis;
     if (current - last > ShenandoahRegionSamplingRate &&
-            Atomic::cmpxchg(current, &_last_sample_millis, last) == last) {
+            Atomic::cmpxchg(&_last_sample_millis, last, current) == last) {
 
       ShenandoahHeap* heap = ShenandoahHeap::heap();
       jlong status = 0;