diff --git a/clang/docs/doxygen.cfg.in b/clang/docs/doxygen.cfg.in
--- a/clang/docs/doxygen.cfg.in
+++ b/clang/docs/doxygen.cfg.in
@@ -384,7 +384,7 @@
 # the optimal cache size from a speed point of view.
 # Minimum value: 0, maximum value: 9, default value: 0.
 
-LOOKUP_CACHE_SIZE      = 2
+LOOKUP_CACHE_SIZE      = 3
 
 #---------------------------------------------------------------------------
 # Build related configuration options
diff --git a/llvm/docs/doxygen.cfg.in b/llvm/docs/doxygen.cfg.in
--- a/llvm/docs/doxygen.cfg.in
+++ b/llvm/docs/doxygen.cfg.in
@@ -385,7 +385,7 @@
 # the optimal cache size from a speed point of view.
 # Minimum value: 0, maximum value: 9, default value: 0.
 
-LOOKUP_CACHE_SIZE      = 2
+LOOKUP_CACHE_SIZE      = 4
 
 #---------------------------------------------------------------------------
 # Build related configuration options