update with a few more links

web server uses multiple <CODE>Listen</CODE> statements to listen on

either multiple ports or multiple addresses.  In order to test each

socket to see if a connection is ready Apache uses <CODE>select(2)</CODE>.

<CODE>select(2)</CODE> indicates that a socket has <EM>none</EM> or

<CODE>select(2)</CODE> indicates that a socket has <EM>zero</EM> or

<EM>at least one</EM> connection waiting on it.  Apache's model includes

multiple children, and all the idle ones test for new connections at the

same time.  A naive implementation looks something like this

properly implement the HTTP protocol.  The second occurs because the

Common Log Format dictates that the log record include a timestamp of the

end of the request.  A custom logging module could eliminate one of the

calls.

calls.  Or you can use a method which moves the time into shared memory,

see the <a href="#patches">patches section below</a>.

<P>As described earlier, <CODE>Rule STATUS=yes</CODE> causes two

<CODE>gettimeofday</CODE> calls and a call to <CODE>times</CODE>:

That's 19 system calls, of which 4 remain relatively easy to remove,

but don't seem worth the effort.

<h3><a name="patches">Appendix: Patches Available</a></h3>

There are

<a href="http://www.arctic.org/~dgaudet/apache/1.3/">

several performance patches available for 1.3.</a>  But they may

be slightly out of date by the time Apache 1.3.0 has been released,

it shouldn't be difficult for someone with a little C knowledge to

update them.  In particular:

<ul>

<li>A 

<a href="http://www.arctic.org/~dgaudet/apache/1.3/shared_time.patch">

patch</a> to remove all <code>time(2)</code> system calls.

<li>A

<a href="http://www.arctic.org/~dgaudet/apache/1.3/mod_include_speedups.patch">

patch</a> to remove various system calls from <code>mod_include</code>,

these calls are used by few sites but required for backwards compatibility.

<li>A

<a href="http://www.arctic.org/~dgaudet/apache/1.3/top_fuel.patch">

patch</a> which integrates the above two plus a few other speedups at the

cost of removing some functionality.

</ul>

<H3>Appendix: The Pre-Forking Model</H3>

<P>Apache (on Unix) is a <EM>pre-forking</EM> model server.  The

<P>Apache's core code is already multithread aware, and Apache version

1.3 is multithreaded on NT.  There have been at least two other experimental

implementations of threaded Apache (one using the 1.3 code base on DCE,

implementations of threaded Apache, one using the 1.3 code base on DCE,

and one using a custom user-level threads package and the 1.0 code base,

neither are available publically).  Part of our redesign for version 2.0

neither are available publically.  There is also an experimental port of

Apache 1.3 to <a href="http://www.mozilla.org/docs/refList/refNSPR/">

Netscape's Portable Run Time</a>, which

<a href="http://www.arctic.org/~dgaudet/apache/2.0/">is available</a>

(but you're encouraged to join the

<a href="http://dev.apache.org/mailing-lists">new-httpd mailing list</a>

if you intend to use it).

Part of our redesign for version 2.0

of Apache will include abstractions of the server model so that we

can continue to support the pre-forking model, and also support various

threaded models.