diff --git a/cmake/pika_setup_allocator.cmake b/cmake/pika_setup_allocator.cmake
index 5e358edc4..f7adb3b51 100644
--- a/cmake/pika_setup_allocator.cmake
+++ b/cmake/pika_setup_allocator.cmake
@@ -90,6 +90,10 @@ if(NOT TARGET pika_dependencies_allocator)
         )
       endif()
       set(_use_custom_allocator TRUE)
+
+      pika_warn(
+        "pika is using mimalloc as the allocator. Typically, exporting the following environment variables will further improve performance: MIMALLOC_EAGER_COMMIT_DELAY=0 and MIMALLOC_LARGE_OS_PAGES=1."
+      )
     endif()
 
     # ##########################################################################