diff --git a/ipykernel/kernelbase.py b/ipykernel/kernelbase.py
index 59f69bc00..30ab173f6 100644
--- a/ipykernel/kernelbase.py
+++ b/ipykernel/kernelbase.py
@@ -76,6 +76,8 @@ class Kernel(SingletonConfigurable):
     # attribute to override with a GUI
     eventloop = Any(None)
 
+    processes: t.Dict[str, psutil.Process] = {}
+
     @observe("eventloop")
     def _update_eventloop(self, change):
         """schedule call to eventloop from IOLoop"""
@@ -953,10 +955,8 @@ async def debug_request(self, stream, ident, parent):
         reply_msg = self.session.send(stream, "debug_reply", reply_content, parent, ident)
         self.log.debug("%s", reply_msg)
 
-    # Taken from https://github.com/jupyter-server/jupyter-resource-usage/blob/e6ec53fa69fdb6de8e878974bcff006310658408/jupyter_resource_usage/metrics.py#L16
     def get_process_metric_value(self, process, name, attribute=None):
         try:
-            # psutil.Process methods will either return...
             metric_value = getattr(process, name)()
             if attribute is not None:  # ... a named tuple
                 return getattr(metric_value, attribute)
@@ -971,12 +971,22 @@ async def usage_request(self, stream, ident, parent):
         reply_content = {"hostname": socket.gethostname(), "pid": os.getpid()}
         current_process = psutil.Process()
         all_processes = [current_process] + current_process.children(recursive=True)
-        process_metric_value = self.get_process_metric_value
+        # Ensure 1) self.processes is updated to only current subprocesses
+        # and 2) we reuse processes when possible (needed for accurate CPU)
+        self.processes = {
+            process.pid: self.processes.get(process.pid, process) for process in all_processes
+        }
         reply_content["kernel_cpu"] = sum(
-            [process_metric_value(process, "cpu_percent", None) for process in all_processes]
+            [
+                self.get_process_metric_value(process, "cpu_percent", None)
+                for process in self.processes.values()
+            ]
         )
         reply_content["kernel_memory"] = sum(
-            [process_metric_value(process, "memory_info", "rss") for process in all_processes]
+            [
+                self.get_process_metric_value(process, "memory_info", "rss")
+                for process in self.processes.values()
+            ]
         )
         cpu_percent = psutil.cpu_percent()
         # https://psutil.readthedocs.io/en/latest/index.html?highlight=cpu#psutil.cpu_percent