diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
index 99aa72e5e9cfadcc2fbfa5aef472a52bb9f41259..fb1f4a984e632d36a0f7cbe5eec00c400cd8ee4f 100644
--- a/tools/perf/Documentation/perf-config.txt
+++ b/tools/perf/Documentation/perf-config.txt
@@ -426,6 +426,11 @@ pager.*::
 		When the subcommand is run on stdio, determine whether it uses
 		pager or not based on this value. Default is 'unspecified'.
 
+kmem.*::
+	kmem.default::
+		This option decides which allocator is to be analyzed if neither
+		'--slab' nor '--page' option is used. Default is 'slab'.
+
 SEE ALSO
 --------
 linkperf:perf[1]