add upgrade note

diff --git a/docs/upgrading.rst b/docs/upgrading.rst
index 30113df9b3c33b35bf40b075392f904edd7bca21..9da936e04273666b836ba16111abe54007ff53df 100644 (file)
--- a/docs/upgrading.rst
+++ b/docs/upgrading.rst
@@ -11,6 +11,12 @@ upgrade notes if your version is older than 3.4.2.
 4.3.x to 4.4.0
 --------------
 
+Latency calculation changes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+It turned out that average latency calculations in earlier versions used integers instead of doubles, which led to the throwing away of any data points between 'the current average' and 1000ms above it, instead of having those data points affecting the average.
+In 4.4.0, we `started using doubles for this <https://github.com/PowerDNS/pdns/pull/9768/files>`__, which means the latency calculation is accurate now.
+
 MySQL character set detection
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^