--- IO-AIO/bin/treescan	2011/09/27 12:10:29	1.7
+++ IO-AIO/bin/treescan	2011/09/27 12:12:55	1.8
@@ -66,7 +66,7 @@
    };
 }
 
-IO::AIO::max_outstanding 400;
+IO::AIO::max_outstanding 400; # two fds per directory, so limit accordingly
 IO::AIO::min_parallel 20;
 
 for my $seed (@ARGV) {