add pyperformance information

Author: gpshead

peps/pep-0830.rst

@@ -202,12 +202,31 @@ Performance Measurements
 
 The pyperformance suite has been run on the merge base, on the PR branch with
 the feature disabled, and on the PR branch with the feature enabled in both
-``ns`` and ``iso`` modes.
+``us`` and ``iso`` modes.
 
-TODO(@gpshead): summarize results of the most recent run here.
+There were no significant performance changes observed by this author. Just
+occasional varying 1-2% measurement noise that could not be reliably
+reproduced.  Below the benchmarking setup noise threshold as far as the author
+is concerned.
 
-TODO(@gpshead): Do another run with the feature enabled but without the StopIteration special case to demonstrate why that choice was made.
+What about the special case performance optimiaztion?  If I omit the two line
+special case to avoid collecting timestamps on ``StopIteration`` and
+``StopAsyncIteration`` in ``Objects/exception.c``, only a single benchmark
+showed a regression: ``async_generators``. That one would reliably run on the
+order of 10% slower without that optimization.  It is likely effectively a
+microbenchmark that does not reflect most application behavior.  Regardless, it
+demonstrates the importance of that optimization.
 
+I used ``configure --enable-optimizations`` builds for my benchmarks and ran
+them using commands such as:
+
+.. code-block:: text
+
+    pyperformance run -p baseline-3a7df632c96/build/python -o baseline-eopt.json
+    pyperformance run -p traceback-timestamps/build/python -o traceback-timestamps-default-eopt.json
+    PYTHON_TRACEBACK_TIMESTAMPS=1 pyperformance run --inherit-environ PYTHON_TRACEBACK_TIMESTAMPS -p traceback-timestamps/build/python -o traceback-timestamps-env=1-eopt.json
+    PYTHON_TRACEBACK_TIMESTAMPS=iso pyperformance run --inherit-environ PYTHON_TRACEBACK_TIMESTAMPS -p traceback-timestamps/build/python -o traceback-timestamps/Results.silencio/traceback-timestamps-env=iso-eopt.json
+    PYTHON_TRACEBACK_TIMESTAMPS=1 pyperformance run --inherit-environ PYTHON_TRACEBACK_TIMESTAMPS -p traceback-timestamps-without-StopIter-cases/build/python -o traceback-timestamps/Results.silencio/traceback-timestamps-without-StopIter-cases-env=1-eopt.json
 
 
 Backwards Compatibility