warn about FAQ of trying to decrease thread stack size with ThreadStackSize

on Linux.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1057049 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/docs/manual/mod/mpm_common.xml b/docs/manual/mod/mpm_common.xml
index 602195335c3cd10b0a0f07791afabdf8d41c2906..16ac26606beecaded39b5184a5264e487b0fd1d5 100644 (file)
--- a/docs/manual/mod/mpm_common.xml
+++ b/docs/manual/mod/mpm_common.xml
@@ -741,6 +741,12 @@ client connections</description>
       The minimum required stack size strongly depends on the modules
       used, but any change in the web server configuration can invalidate
       the current <directive>ThreadStackSize</directive> setting.</li>
+
+      <li>On Linux, this directive can only be used to increase the default
+      stack size, as the underlying system call uses the value as a 
+      <em>minimum</em> stack size.  The (often large) soft limit for 
+      <code>ulimit -s</code> (8MB if unlimited) is used as the default stack 
+      size.</li>
     </ul>
 
     <note>It is recommended to not reduce <directive>ThreadStackSize</directive>