libertus

As seen on the Weblog Tools Collection, Investigating WordPress 2.0.4 Performance and Memory Usage in WordPress 2.0.2.

With a one-line change to the WordPress core code, this plugin gathers readings of WordPress use of memory, time and database queries which it dumps to a compressed file for later analysis. The core code change enables a reading to be taken each time WP calls do_action(), and looks like this:

function do_action($tag, $arg = '') {
  if( $tag != 'do_action' ) do_action( 'do_action', $tag );

You don’t need to make this core change for the plugin to work, but without the change the plugin can only take a single reading at the end of the WP run. This can still be useful.

performance-probe.php. Use at your own risk.

Further Reading

As I find interesting and/or useful stuff on the net about WP performance, I’ll link here.

WP Queries: a short review

Some performance analysis and tuning against WP SQL queries.

measuring WordPress performance

By _ck_ on #wordpress. Links to some useful performance and diagnostic tools. Also links back here

WP Performance Graph

A developing Python script using rrdtool to produce a running graph from the output of my plugin. Neat.

8 Responses

1. _ck_ said: August 13th, 2006 at 05:12

   Hey take a look at this too: http://blog.rompe.org/node/85
   I wasn’t aware of the getrusage function, might give more useful info than just memory_get_usage.

   Reply

2. Libertus said: August 13th, 2006 at 10:08

   I wasn’t aware of that function either. Thanks for the link. I’ll investigate…

   Reply

3. westi said: September 13th, 2006 at 09:17

   Rather than hacking a core file can you not use the special (and probably undocumented) “all” action which gets called for all do_action (and apply_filters) calls. It needs careful use because it runs on all the filter calls (which include the options) but that should make the plugin self contained then.

   Reply

   1. Libertus said: September 13th, 2006 at 10:48

      Hi Westi,

      I found and tried the “all” hook during development of the probe. As you point out, it hooks filters also, which made the probe too intrusive for my purposes, so I didn’t explore that route.

      I would love to make the probe self-contained. If a “do_action” hook isn’t destined for the core, perhaps I’ll examine the “all” hook again.

      Or maybe the Open Source muse will smile and someone else will fix it for me.

      Reply

4. Ajay D'Souza said: September 13th, 2006 at 10:21

   Hi,

   This seems a good plugin. I haven’t yet installed it. I just wanted to know is how exactly do you read the output file.

   Ajay

   Reply

   1. Libertus said: September 13th, 2006 at 12:11

      Hi Ajay,

      The plugin (with the core do_action() mod) builds an array during the course of the WP run. Each entry in the array is created when WP calls “do_action”. At that point, the current time, memory usage, database query count and do_action() tag are appended to the array. At shutdown, the array is written out serialized and (unnecessarily!) gzipped to a timestamped file.

      My accompanying dump program reads the serialized array from a file and writes out each entry in CSV format as follows:

      Field 1 is the sequence number
      Field 2 is the tag passed to do_action()
      Field 3 is the value of memory_get_usage() when the hook was called
      Field 4 is the change in memory usage from the previous reading
      Field 5 is the run time so far, returned from timer_stop()
      Field 6 is the number of database queries (from $wpdb->num_queries)

      The final record is special, in that it is generated during shutdown. Field 2 on the final record contains the REQUEST_URI passed to WP, so you know which page generated the probe file.

      Reply

5. mustaq said: September 15th, 2006 at 07:26

   hii

   i get this error

   Cannot modify header information - headers already sent by (output started at C:\netserve\www\wblog\wp-content\plugins\performance-probe.php:92) in C:\netserve\www\wblog\wp-includes\pluggable-functions.php on line 272

   Fatal error: Call to undefined function: memory_get_usage() in C:\netserve\www\wblog\wp-content\plugins\performance-probe.php on line 53

   Reply

   1. Libertus said: September 15th, 2006 at 10:37

      outreach

      • none
      • ~

      Hi Mustaq,

      I’ve experienced this problem before, and I know of no way to overcome it. The performance probe primarily tracks the amount of memory used. The PHP you are using was compiled without memory limits, so the built-in function to get the amount of memory used is not available.

      The PHP manual entry for memory_get_usage() has more details, including various workarounds, none of which are acceptable because they run external programs and would disturb the performance statistics being measured.

      Reply