diff --git a/avalanche/evaluation/metrics/disk_usage.py b/avalanche/evaluation/metrics/disk_usage.py
index a2a92149e..c0cbd5046 100644
--- a/avalanche/evaluation/metrics/disk_usage.py
+++ b/avalanche/evaluation/metrics/disk_usage.py
@@ -10,6 +10,9 @@
 ################################################################################
 
 import os
+import time
+from sys import platform
+import subprocess
 from pathlib import Path
 from typing import Union, Sequence, List, Optional
 
@@ -45,6 +48,8 @@ def __init__(
             paths_to_monitor = [paths_to_monitor]
 
         self._paths_to_monitor: List[str] = [str(p) for p in paths_to_monitor]
+        # this is used to avoid sending multiple warnings
+        self._warning_sent = False
 
         self.total_usage: float = 0.0
 
@@ -57,7 +62,7 @@ def update(self):
 
         dirs_size = 0.0
         for directory in self._paths_to_monitor:
-            dirs_size += DiskUsage.get_dir_size(directory)
+            dirs_size += self.get_dir_size(directory)
 
         self.total_usage = dirs_size
 
@@ -81,8 +86,7 @@ def reset(self) -> None:
         """
         self.total_usage = 0
 
-    @staticmethod
-    def get_dir_size(path: str) -> float:
+    def get_dir_size(self, path) -> float:
         """
         Obtains the size of the given directory, in KiB.
 
@@ -90,15 +94,36 @@ def get_dir_size(path: str) -> float:
         :return: A float value describing the size (in KiB)
             of the directory as the sum of all its elements.
         """
+
+        start = time.time()
         total_size = 0.0
-        for dirpath, dirnames, filenames in os.walk(path):
-            for f in filenames:
-                fp = os.path.join(dirpath, f)
-                # skip if it is symbolic link
-                if not os.path.islink(fp):
-                    # in KB
-                    s = os.path.getsize(fp) / 1024
-                    total_size += s
+
+        if platform == "linux" or platform == "linux2":
+            total_size = (
+                float(
+                    subprocess.check_output(["du", "-sb", path])
+                    .split()[0]
+                    .decode("utf-8")
+                )
+                / 1024
+            )
+        else:
+            for dirpath, dirnames, filenames in os.walk(path):
+                for f in filenames:
+                    fp = os.path.join(dirpath, f)
+                    # skip if it is symbolic link
+                    if not os.path.islink(fp):
+                        # in KB
+                        s = os.path.getsize(fp) / 1024
+                        total_size += s
+
+        end = time.time()
+        elapsed_t = end - start
+        # if we wait for more than 1 sec.
+        if elapsed_t > 0.5 and self._warning_sent is False:
+            print(f"\n\nWARNING: Time to get size of {path}: {elapsed_t}")
+            print("Are you sure you want to monitor this directory?\n")
+            self._warning_sent = True
 
         return total_size
 
@@ -132,10 +157,7 @@ def __init__(self, paths_to_monitor):
         Creates an instance of the minibatch Disk usage metric.
         """
         super(MinibatchDiskUsage, self).__init__(
-            paths_to_monitor,
-            reset_at="iteration",
-            emit_at="iteration",
-            mode="train",
+            paths_to_monitor, reset_at="iteration", emit_at="iteration", mode="train"
         )
 
     def __str__(self):
@@ -177,10 +199,7 @@ def __init__(self, paths_to_monitor):
         Creates an instance of the experience Disk usage metric.
         """
         super(ExperienceDiskUsage, self).__init__(
-            paths_to_monitor,
-            reset_at="experience",
-            emit_at="experience",
-            mode="eval",
+            paths_to_monitor, reset_at="experience", emit_at="experience", mode="eval"
         )
 
     def __str__(self):
@@ -214,7 +233,7 @@ def disk_usage_metrics(
     minibatch=False,
     epoch=False,
     experience=False,
-    stream=False
+    stream=False,
 ) -> List[DiskPluginMetric]:
     """
     Helper method that can be used to obtain the desired set of
diff --git a/tests/evaluation/test_disk_usage.py b/tests/evaluation/test_disk_usage.py
new file mode 100644
index 000000000..dbd6dfeff
--- /dev/null
+++ b/tests/evaluation/test_disk_usage.py
@@ -0,0 +1,17 @@
+""" Disk Usage Metric Test"""
+
+import unittest
+
+from avalanche.evaluation.metrics import DiskUsage
+
+
+class DiskUsageTests(unittest.TestCase):
+    def test_basic(self):
+        """just checking that directory size is computed without errors."""
+
+        disk = DiskUsage()
+        disk.get_dir_size(".")
+
+
+if __name__ == "__main__":
+    unittest.main()