[tools] Permit benchmark experiments without boost control (RobotLoco…

…motion#21640)

Contemporary AMD processors have a frequency boost feature, called
"Precision Boost". Sadly, the Linux kernel driver configuration as of
Ubuntu Jammy + Linux 6.5 does not expose boost control. Some user land
control does appear to be promised for future kernels.

In the mean time, this patch permits benchmark experiments to run, but
prints a console warning that results may be noisy.

tools/performance/benchmark_tool.py

@@ -70,6 +70,20 @@ def sudo(*args, quiet=False):
         subprocess.run(new_args, stderr=subprocess.STDOUT, check=True)
 
 
+class NoBoost:
+    def is_supported(self):
+        return True
+
+    def get_boost(self):
+        """Return the current boost state; True means boost is enabled."""
+        return False
+
+    def set_boost(self, boost_value):
+        """Set the boost state; True means boost is enabled."""
+        say("No method of cpu boost control was found;"
+            " nothing is changed. Benchmark results may be noisy.")
+
+
 class IntelBoost:
     # This is the Linux kernel configuration file for Intel's "turbo boost".
     # https://www.kernel.org/doc/html/v4.12/admin-guide/pm/intel_pstate.html#no-turbo-attr
@@ -114,7 +128,7 @@ class CpuSpeedSettings:
     """Routines for controlling CPU speed."""
     def __init__(self):
         self._boost = None
-        for boost in [LinuxKernelBoost, IntelBoost]:
+        for boost in [LinuxKernelBoost, IntelBoost, NoBoost]:
             if boost().is_supported():
                 self._boost = boost()