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<html>
<head><title>Apache::ASP Site Tuning</title></head>
<body bgcolor=white>

<blockquote>
Note: this article was from a series running on PerlMonth from 1999.
PerlMonth.com seems to have disappeared, so this article is reposted
with some slight modifications to make it current for recent releases
of Apache::ASP ( versions >= 2.29 ).
</blockquote>

<h2>Apache::ASP Site Tuning</h2>
by Joshua Chamas <i>&lt;chamas&nbsp;at&nbsp;alumni.stanford.org&gt;</i>
<p>



Last month, we used Apache::ASP to build a simple 
<a href=http://www.apache-asp.org/apps/bookmarks/>MyBookmarks</a>
web application.  Now we are going to tune the 
<a href=http://www.apache-asp.org/>Apache::ASP</a> web application and 
<a href=http://www.apache.org>Apache</a> web server, taking a mild mannered 
web app running at <tt>250,000</tt> pages per day, and boosting it up 4 times 
to a <tt>1,000,000</tt> pages per day powerhouse.
<p>
Are you ready? <font size=+1>Let's Tune!</font>
<p>

<h3>Methodology</h3>
The application was taken as it was built last week,
and incrementally benchmarked, changing one configuration
setting at a time, and showing the performance changes 
below.  The URL tested is the main URL of the application,
<a href=http://www.apache-asp.org/apps/bookmarks/index.asp
  >.../bookmarks/index.asp</a>.
<p>
The application is run on a Solaris x86 box, PII300 512K cache
with 2 4G 7200 RPM SCSI drives in a software RAID 1 configuration.  
The following numbers are not meant to be compared against
other web application environments, or systems, but show 
relative performance improvements when tuning Apache::ASP 
and Apache on this particular system.
<p>
The web server software being tested is apache 1.3.4, with 
the testing client <tt>ab</tt>, or ApacheBench, 
run locally on the server.  Because ApacheBench does not support
cookies, a new Apache::ASP $Session is created in StateDir
for every request, so that the benchmark numbers are worse 
than what you would see in a production setting.  Obviously testing locally
does not take into account many slow client connections
over the internet, which would likely be offset by a reverse
proxy accelerator in production 
(<a href=http://perl.apache.org/guide>see mod_perl guide</a>).
<p>
The <tt>ab</tt> program was run with 5 concurrent clients for 
30 seconds with the following command:
<pre>
  ab -c 5 -t 30 http:// $HOST /bookmarks/index.asp
</pre>

<h3>Tuning</h3>

After running the first bench, and watching the system under
top, it becomes strikingly clear that disk i/o is the bottleneck,
with 50%+ of the time spent waiting for disk.  The reason
is that state management for $Session and $Application uses
SDBM_File, or optionally DB_File, databases on disk to store data, 
and is highly i/o intensive.
<p>
The <i>trick</i> then is to relocate the <tt>StateDir</tt> 
to a fast cached file system.  On Solaris, this happens to 
be /tmp/... by default, but on Linux and WinNT, the file systems seem
to be cached automatically, so you may not need to do anything
except locate <tt>StateDir</tt> to a secure, non-browsable, location.
Using a cached or RAM file system will also spare your disk, which is good 
as it is often the first thing to go on your box.



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+116%
	</tt>
</b></td>
<td bgcolor=yellow><tt>6.5 h/s</tt></td>
<td bgcolor=yellow><tt>14.1 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=#c0c0c0>AP.htaccess</td>
	<td bgcolor=#c0c0c0>yes</td>
	<td bgcolor=#c0c0c0>yes</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxRequestsPerChild</td>
	<td bgcolor=#c0c0c0>50</td>
	<td bgcolor=#c0c0c0>50</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Debug</td>
	<td bgcolor=#c0c0c0>1</td>
	<td bgcolor=#c0c0c0>1</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionSerialize</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=pink>StateDir</td>
	<td bgcolor=pink>.state</td>
	<td bgcolor=pink>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1>Disk i/o activity takes 50% of the time, because the StateDir is pointed at a non-caching file system.</font></td>
	<td><font size=-1>Disk i/o activity is nearly 0%, with roughly 75% of the time spent in the user space, and 25% in the kernel</font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>

More straightforward is turning off debugging.  
The Apache::ASP code has been streamlined for production
when debugging is turned off, and there is a significant
penalty for leaving it on, as well as a bunch of clutter
in your error_log.  



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+12%
	</tt>
</b></td>
<td bgcolor=yellow><tt>14.1 h/s</tt></td>
<td bgcolor=yellow><tt>15.8 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=#c0c0c0>AP.htaccess</td>
	<td bgcolor=#c0c0c0>yes</td>
	<td bgcolor=#c0c0c0>yes</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxRequestsPerChild</td>
	<td bgcolor=#c0c0c0>50</td>
	<td bgcolor=#c0c0c0>50</td>
	</tr>

	<tr>
	<td bgcolor=pink>Debug</td>
	<td bgcolor=pink>1</td>
	<td bgcolor=pink>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionSerialize</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>StateDir</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1>Disk i/o activity is nearly 0%, with roughly 75% of the time spent in the user space, and 25% in the kernel</font></td>
	<td><font size=-1></font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>

Those were the two big basic tunes for Apache::ASP.
Let's now go to the Apache web server.  So far, our
configuration information has been stored in a .htaccess
file, which must be reparsed every request by Apache.
So, we move the configuration information into one of 
the *.conf configuration files, to avoid that per
request overhead.  Also make sure to disallow .htaccess
file parsing on up the file tree by setting an 

<pre>
  AllowOverride None
</pre>

wherever your Apache::ASP application is located.



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+9%
	</tt>
</b></td>
<td bgcolor=yellow><tt>15.8 h/s</tt></td>
<td bgcolor=yellow><tt>17.3 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=pink>AP.htaccess</td>
	<td bgcolor=pink>yes</td>
	<td bgcolor=pink>no</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxRequestsPerChild</td>
	<td bgcolor=#c0c0c0>50</td>
	<td bgcolor=#c0c0c0>50</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Debug</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionSerialize</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>StateDir</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1></font></td>
	<td><font size=-1>Couldn't believe my eyes when I saw there to be so little difference when not using .htaccess.  My guess is that the Apache people optimized this at some point.</font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>

The MaxRequestsPerChild is commonly overlooked in 
web server setup.  What this does is control the
number of requests that a child httpd server may
serve before exiting, and the parent reforking 
another one.  With mod_perl library loading
and script recompilations, a fork is no small thing,
and avoiding the fork penalty is important.
<p>
We had the MaxRequestsPerChild pretty low before 
at 50 but we up it now to 500 which should be fine
for production.  You don't want to set this too high,
or the mod_perl httpds will often take up too much
memory because of leaks, and shared forked code
becoming unshared as it gets dirtied.



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+31%
	</tt>
</b></td>
<td bgcolor=yellow><tt>17.3 h/s</tt></td>
<td bgcolor=yellow><tt>22.8 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=#c0c0c0>AP.htaccess</td>
	<td bgcolor=#c0c0c0>no</td>
	<td bgcolor=#c0c0c0>no</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=pink>APMaxRequestsPerChild</td>
	<td bgcolor=pink>50</td>
	<td bgcolor=pink>500</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Debug</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionSerialize</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>StateDir</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1>Couldn't believe my eyes when I saw there to be so little difference when not using .htaccess.  My guess is that the Apache people optimized this at some point.</font></td>
	<td><font size=-1>This bench only had 684 requests, so there was no parent httpd forking during this time, whereas before there may have been reforking every few seconds during the 30 second bench.</font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>

Back to Apache::ASP, and some finer tuning.  By
default SessionSerialize is 0, and we are going
to turn it on.  What this does is lock $Session
for exclusive use during the course of the script
being run, so that any reads or writes to $Session
don't have to lock it every time.  Because of the i/o
requirements of SDBM_File, each time $Session is read from
or written to, it is freshly tied to the 
database and locked, so to avoid these ties can save much.
<p>
The reason why SessionSerialize is not enabled
by default is that one could easily deny service
to a user with a long running script, such that no
other scripts for that same user $Session could be run,
and this requires some expertise.
Also SessionSerialize is probably not a good thing 
for framed sites, where there is greater concurrency 
for the same $Session.



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+12%
	</tt>
</b></td>
<td bgcolor=yellow><tt>22.8 h/s</tt></td>
<td bgcolor=yellow><tt>25.74 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=#c0c0c0>AP.htaccess</td>
	<td bgcolor=#c0c0c0>no</td>
	<td bgcolor=#c0c0c0>no</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxRequestsPerChild</td>
	<td bgcolor=#c0c0c0>500</td>
	<td bgcolor=#c0c0c0>500</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Debug</td>
	<td bgcolor=#c0c0c0>0</td>
	<td bgcolor=#c0c0c0>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=pink>SessionSerialize</td>
	<td bgcolor=pink>0</td>
	<td bgcolor=pink>1</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>StateDir</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	<td bgcolor=#c0c0c0>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1>This bench only had 684 requests, so there was no parent httpd forking during this time, whereas before there may have been reforking every few seconds during the 30 second bench.</font></td>
	<td><font size=-1></font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>



















From start to finish, we have nearly quadrupled the
speed of the web application, and thus the site's
ability to serve up web pages.  This one should handle
just about 1,000,000 page views per day. :) 



<center>
<p>
<table border=0 bgcolor=gray>

<tr bgcolor=white>
<td><b>Hits/sec</b></td>
<td align=center><b>Before</b></td>
<td align=center><b>After</b></td>
</tr>

<tr>
<td bgcolor=#bbccff>
	<tt>
	+296%
	</tt>
</b></td>
<td bgcolor=yellow><tt>6.5 h/s</tt></td>
<td bgcolor=yellow><tt>25.74 h/s</tt></td>
</tr>
<tr bgcolor=white><td colspan=3><b>Configuration</b></td></tr>

	<tr>
	<td bgcolor=pink>AP.htaccess</td>
	<td bgcolor=pink>yes</td>
	<td bgcolor=pink>no</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>APMaxClients</td>
	<td bgcolor=#c0c0c0>5</td>
	<td bgcolor=#c0c0c0>5</td>
	</tr>

	<tr>
	<td bgcolor=pink>APMaxRequestsPerChild</td>
	<td bgcolor=pink>50</td>
	<td bgcolor=pink>500</td>
	</tr>

	<tr>
	<td bgcolor=pink>Debug</td>
	<td bgcolor=pink>1</td>
	<td bgcolor=pink>0</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>Global</td>
	<td bgcolor=#c0c0c0>.</td>
	<td bgcolor=#c0c0c0>.</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>GlobalPackage</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	<td bgcolor=#c0c0c0>My::Bookmarks</td>
	</tr>

	<tr>
	<td bgcolor=pink>SessionSerialize</td>
	<td bgcolor=pink>0</td>
	<td bgcolor=pink>1</td>
	</tr>

	<tr>
	<td bgcolor=#c0c0c0>SessionTimeout</td>
	<td bgcolor=#c0c0c0>15</td>
	<td bgcolor=#c0c0c0>15</td>
	</tr>

	<tr>
	<td bgcolor=pink>StateDir</td>
	<td bgcolor=pink>.state</td>
	<td bgcolor=pink>/tmp/bookmarks</td>
	</tr>


	<tr bgcolor=white>
	<td><b>Comments</b></td>
	<td><font size=-1>Disk i/o activity takes 50% of the time, because the StateDir is pointed at a non-caching file system.</font></td>
	<td><font size=-1></font></td>
	</tr>

<tr bgcolor=white>
<td><b>Legend</b></td>
<td colspan=2>
<font size=-2 face=verdana>
Configuration items
that start with AP are Apache configuration options, the
rest are Apache::ASP.  The 
.htaccess one means that configurations are stored in the .htaccess
if yes, if no in a configuration file.  The configuration changes
between benchmarks are highlighted in <font color=pink><b>pink</b></font>.
</font>
</td></tr>
</table>
<p>
</center>

For more information on Apache::ASP tuning, see the 
<a href=http://www.apache-asp.org/tuning.html>tuning docs online</a>.

</body>
</html>