per comments, add a better hint about what %D/%T measure / do not measure

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1818344 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/docs/manual/mod/mod_log_config.xml b/docs/manual/mod/mod_log_config.xml
index 0434cdc7ba60cc107da57b603c0d426ea92b37e8..5ccb866057e2a4f5687969049c190dee0a9049a1 100644 (file)
--- a/docs/manual/mod/mod_log_config.xml
+++ b/docs/manual/mod/mod_log_config.xml
@@ -93,7 +93,7 @@
         to the server. Only version 0 cookies are fully supported.</td></tr>
 
     <tr><td><code>%D</code></td>
-        <td>The time taken to serve the request, in microseconds.</td></tr>
+        <td>The time taken to serve the request, in microseconds. See %T for details.</td></tr>
 
     <tr><td><code>%{<var>VARNAME</var>}e</code></td>
         <td>The contents of the environment variable
@@ -225,7 +225,22 @@
         </td></tr>
 
     <tr><td><code>%T</code></td>
-        <td>The time taken to serve the request, in seconds.</td></tr>
+        <td>The time taken to serve the request, in seconds. The time measured
+        begins when the first line of the HTTP request is read from the host
+        operating system by by the HTTP server and ends when the last byte of
+        the response is written by the HTTP server to the host operating system.
+        <p> The time measured does <em>not</em> include any of the following:
+        <ul>
+         <li> Time spent in TCP or TLS handshakes.</li>
+         <li> The time before a webserver thread is able to read the first 
+              line of the request.</li>
+         <li> Delays in the operating system putting the response data out 
+              onto the network.</li>
+         <li> Time taken for the response to arrive at the client host.</li>
+         <li> Time taken for the the useragent to read and process the 
+              response.</li>
+       </ul></p>
+    </td></tr>
 
     <tr><td><code>%{<var>UNIT</var>}T</code></td>
         <td>The time taken to serve the request, in a time unit given by