diff --git a/src/docs/src/maintenance/performance.rst b/src/docs/src/maintenance/performance.rst
index ede86a1ee3a..574952e6b3f 100644
--- a/src/docs/src/maintenance/performance.rst
+++ b/src/docs/src/maintenance/performance.rst
@@ -58,6 +58,14 @@ operations add the following to ``(prefix)/etc/defaults/couchdb``
 
 .. _command line flag +A in erl(1): http://erlang.org/doc/man/erl.html
 
+Since Erlang OTP 21, the linked-in drivers have been migrated to dirty IO schedulers.
+These schedulers can be configured by ``ERL_FLAGS`` environment
+variable. For example, to give Erlang 80 dirty schedulers
+add the following to ``(prefix)/etc/defaults/couchdb``
+(or equivalent)::
+
+    export ERL_FLAGS="+Sdio 80"
+
 System Resource Limits
 ======================