A drop-in replacement for the system.module of Drupal 5.7 which makes your Drupal 5 site use less memory and may even make it faster. The one test that I ran suggested that I got:

• 3% faster performance
  
• 5% less memory

If this sounds interesting, please feel free to install this and try it out. I'd be especially interested to hear feedback as to whether this makes any difference at all if you have an opcode cache installed. If it works for you, you might be interested in downloading my other low memory modules as well.

Performance Benchmark (5.2 version)

This version of the module performs around 3% faster than the stock module in my single test:

Benchmark run on stock Fedora 7 with Apache 2.2.4 (httpd-2.2.4-4.1.fc7) and MySQL 5.0.37 (mysql-server-5.0.37-2.fc7), using ab -n 200 http://hostname/user on a development copy of this site.

The stock system.module:

Requests per second:    3.29 [#/sec] (mean)
Time per request:       304.392 [ms] (mean)
Time per request:       304.392 [ms] (mean, across all concurrent requests)
Transfer rate:          23.64 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:   294  303   8.8    301     339
Waiting:      294  303   8.8    301     338
Total:        294  303   8.8    301     339

The low memory version:

Requests per second:    3.40 [#/sec] (mean)
Time per request:       293.854 [ms] (mean)
Time per request:       293.854 [ms] (mean, across all concurrent requests)
Transfer rate:          24.48 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:   282  293   9.8    290     352
Waiting:      282  292   9.7    290     348
Total:        282  293   9.8    290     352

Memory Benchmark

This module saved 538K memory or 5% of overall site memory usage in the only test I ran.

Using the same setup as above, and testing the same page (the user login page), I added an echo memory_get_usage(); to the end of Drupal's index.php. Without the patch, it printed 11129644, or 10.61MB. With the patch, it printed 10578956, or 10.09MB, a savings of 538K or 5%. This savings won't be realized on the administration pages.

Caveat Emptor

1. This patch removes several functions from system.module which are technically "public" functions by Drupal's convention, because they don't start with an underscore. If you have code which relied on one of those functions that got removed, and you're interested in using this, please leave a comment below.
   
2. I haven't thoroughly tested all of the administration functions covered by the system module. If you run into a problem which you believe to be caused by this module, please also leave a comment below.
3. As this code is based on Drupal, which is licensed under the GPL, this code is also licensed under the GPL, which means (in the word of said license):

   This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
   

Installation (whole module version)

To install, simply download the archive, unpack it, and put the files in your modules/system directory. The system.module from the archive will replace the stock drupal system.module.

If you're on a command line, you can do so by switching into the drupal installation directory (running ls should show index.php and cron.php), and running:

wget -O - http://wtanaka.com/system/files/system-5.7.tar.bz2 | bzcat | tar xvf -

Installation (patch version)

From the drupal installation directory (running ls should show index.php and cron.php), run:

wget -O - http://wtanaka.com/system/files/system-5.7.patch.bz2 | bzcat | patch -p0

Uninstall (patch version)

From the drupal installation directory (running ls should show index.php and cron.php), run:

wget -O - http://wtanaka.com/system/files/system-5.7.patch.bz2 | bzcat | patch -p0 -R
rm -f modules/system/*.inc.php

Attachment	Size
system-5.2.patch.bz2	24.27 KB
system-5.2.tar.bz2	20.12 KB
system-5.3.patch.bz2	24.27 KB
system-5.3.tar.bz2	20.12 KB
system-5.5.patch.bz2	24.25 KB
system-5.5.tar.bz2	20.13 KB
system-5.6.patch.bz2	24.29 KB
system-5.6.tar.bz2	20.17 KB
system-5.7.patch.bz2	24.29 KB
system-5.7.tar.bz2	20.17 KB