diff --git a/python/ray/memory_monitor.py b/python/ray/memory_monitor.py
index c460b22d5..9f52dc725 100644
--- a/python/ray/memory_monitor.py
+++ b/python/ray/memory_monitor.py
@@ -108,8 +108,15 @@ class MemoryMonitor:
                 return  # escape hatch, not intended for user use
 
             self.last_checked = time.time()
-            total_gb = psutil.virtual_memory().total / (1024**3)
-            used_gb = total_gb - psutil.virtual_memory().available / (1024**3)
+            psutil_mem = psutil.virtual_memory()
+            total_gb = psutil_mem.total / (1024**3)
+            used_gb = total_gb - psutil_mem.available / (1024**3)
+
+            # Linux, BSD has cached memory, which should
+            # also be considered as unused memory
+            if hasattr(psutil_mem, "cached"):
+                used_gb -= psutil_mem.cached / (1024**3)
+
             if self.cgroup_memory_limit_gb < total_gb:
                 total_gb = self.cgroup_memory_limit_gb
                 with open("/sys/fs/cgroup/memory/memory.usage_in_bytes",