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From Rich Bowen <>
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
>> </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="">threads</a>?</p>
>> +<p>2. Does the system support <a href="http://en.wikipSo,">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

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

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