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From Rich Bowen <rbo...@rcbowen.com>
Subject Re: svn commit: r1395417 - in /httpd/httpd/trunk/docs/manual: mpm.html.en mpm.xml
Date Mon, 08 Oct 2012 23:37:49 GMT
>> --- httpd/httpd/trunk/docs/manual/mpm.html.en (original)
>> +++ httpd/httpd/trunk/docs/manual/mpm.html.en Sun Oct  7 22:59:14 2012
>> @@ -99,6 +99,28 @@ choice at compile-time.</p>
>>     <code class="module"><a href="./mod/event.html">event</a></code>,
depending on platform capabilities</td></tr>
>> <tr class="odd"><td>Windows</td><td><code class="module"><a
href="./mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
>> </table>
>> +
>> +<div class="note"><p>Here, 'Unix' is used to mean Unix-like operating
systems, such as
>> +Linux, BSD, Solaris, Mac OS X, etc.</p></div>
>> +
>> +<p>In the case of Unix, the decision as to which MPM is installed is
>> +based on two questions:</p>
>> +<p>1. Does the system support <a href="http://en.wikipedia.org/wiki/Threads_(computer_science)">threads</a>?</p>
>> +<p>2. Does the system support <a href="http://en.wikipSo, edia.org/wiki/Polling_(computer_science)">polling</a>?</p>
>> +
>> +<p>If the answer to both questions is 'yes', the default MPM is
>> +<code class="module"><a href="./mod/event.html">event</a></code>.</p>
> 
> It isn't that simple.
> 
> APR_POLLSET_THREADSAFE has to be supported, and that is more than the
> well-known capabilities of threads and polling.
> 
> APR_POLLSET_THREADSAFE means that the platform has an advanced polling
> mechanism which allows pollsets to be manipulated in a certain way,
> and that APR has an implementation that uses that mechanism.
> 
> Linux, Solaris, and FreeBSD/Mac OS X are platforms that satisify both
> characteristics.  z/OS is a platform that has an advanced polling
> mechanism but without an APR implementation in the stable branches.
> Neither AIX nor HP-UX have APR implementations, though I'd guess that
> the OS has the feature and nobody has gotten around to exploiting it
> in APR.


So, how about:

======================================
In the case of Unix, the decision as to which MPM is installed by default is based on two
questions:

1. Does the system support threading?
2. Does the system support APR_POLLSET_THREADSAFE?

Linux, Solaris, FreeBSD and Mac OS X are platforms that satisfy both characteristics.

If the answer to both questions is 'yes', the default MPM is event.

If The answer to #1 is 'yes', but the answer to #2 is 'no', the default will be worker.

If the answer to both questions is 'no', then the default MPM will be prefork.

(strike last sentence)
=========================================

Or, is it better to leave off the details entirely? I thought it would be good to give folks
an idea of what the default are. For most people, the default will presumably be event ...
except when it's not. Right?


-- 
Rich Bowen
rbowen@rcbowen.com :: @rbowen
rbowen@apache.org







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