WordPress
Performance & Scalability
Joseph Scott
http://josephscott.org/

Find Me
• http://josephscott.org/
• joseph@josephscott.org
• http://twitter.com/josephscott/
• #wordpress-dev

Backup First

Performance
Shelby Supercars Ultimate Aero Twin Turbo

Scalability

Web Apps Are Like
Ogres Onions

Start At The Bottom
Deal with network
problems / bottlenecks
first
Be familiar with Operating
System network
optimizations

Web Server
Apache?

Web Server
nginx LiteSpeed
http://nginx.net/ http://litespeedtech.com/
lighttpd Zeus
http://www.lighttpd.net/ http://www.zeus.com/

Apache
• Can be a pig, remove any modules you aren’t
using
• Turn off host name lookups
• Turn on compression (mod_deflate)
• Turn off FollowSymLinks (and .htaccess if you
can)
• Skip Apache all together, serve static content
from another server

PHP
• Use an opcode cache (APC, lots of others)
• Don’t use on static files (unless you really,
really need to)
• Consider output buffering
• Be careful with preg_* functions

MySQL - Table Types
MyISAM
• High performance reads or writes, not
both
• Full text search
InnoDB
• Better for mixed reads/writes
• Transactions, Foreign Keys

MySQL
• Double (and triple) check indexes
• Tune your configuration
• key_buffer_size, table_cache,
sort_buffer_size, read_buffer_size
• Replication (more on that later)
• Interesting quirks, get familiar with them

Memcache
In memory object cache, learn it, use it, love it
With Caution

WordPress
• MySQL tables default to using MyISAM,
consider using InnoDB instead
• Turn off unused plugins
• Check that themes and plugins aren’t abusing
MySQL or PHP
• Server static content from another server
(optimized for that task)

Construction
Start from the bottom and
work your way up

Test Setup
• Ubuntu 9.04 server edition
• Apache 2.2.11
• PHP 5.2.6
• MySQL 5.0.75
• WordPress -trunk

Test “Hardware”
Parallels 4.0
2.66 Xeon
1 GB Ram

Abusing The Server
siege - http://www.joedog.org/index/siege-home
siege -d 1 -c 50 -r 10 http://192.168.1.100/

Below The Baseline
Zero Byte HTML - zero.html
(80 r/s) ~0.01 s/r
Zero Byte PHP - zero.php
(80 r/s) ~0.01 s/r

a phpinfo( )’s worth
51,213 / 8,689 bytes
static HTML - phpinfo.html
100% (75 r/s) ~0.04 s/r
PHP - phpinfo.php
92% (69 r/s) ~0.04 s/r

Hello World!
6,582 / 2,531 bytes
WordPress: /wp/?p=1

Hello World!
6,582 / 2,531 bytes
WordPress: /wp/?p=1
8% (6 r/s) ~7 s/r

Hello World!
+ APC
WordPress: /wp/?p=1
29% (22 r/s) ~1.51 s/r

Use An Opcode Cache!
%8 ~7 %29 ~1.51

Use An Opcode Cache!
%8 ~7 %29 ~1.51

WordPress + Memcache
• Ryan Boren
• Stores WordPress data in Memcache
• Reduces the number of database queries
• http://ryan.wordpress.com/2005/12/23/
memcached-backend/

Hello World!
+ APC + Memcache
WordPress: /wp/?p=1
32% (24 r/s) ~1.4 s/r

Batcache!

WordPress + Batcache
• Andy Skelton
• Stores rendered HTML in Memcache
• http://wordpress.org/extend/plugins/batcache/

Hello World! + APC +
Memcache + Batcache
WordPress: /wp/?p=1
80% (60 r/s) ~0.4 s/r

Hello World! + APC +
Memcache + Batcache

WordPress
+ WP Super Cache
• Donncha O Caoimh
• Stores rendered HTML on disk
• http://wordpress.org/extend/plugins/wp-super-
cache/

Let me 'splain. ...
No, there is too much. Let me sum up.
Requests Seconds per
Description Potential
per Second request (mean)
Zero Bytes 80 ~0.01 -
Static phpinfo() 75 ~0.04 100%
phpinfo() 69 ~0.04 92%
OOB WP 6 ~7.00 8%
WP & APC 22 ~1.51 29%
WP & APC/
24 ~1.40 32%
Memcache
WP & APC/
60 ~0.04 80%
Memcache/Batcache

What Now?

All In One
Web / Database

Moving Out
Web Database

Paying In Cache
Web
Memcache Database

But Wait, There’s More!

MySQL Replication
• Master / Slave - one way asynchronous
• Send writes to the master, reads to the
slave(s)
• Replication works on both MyISAM and
InnoDB tables
• Supports multiple slaves and replication
chaining

Enter HyperDB
• Drop in replacement for the default
WordPress database class
• Supports distributed reads/writes
• Partition data (helpful for large WPMU
installs)
• Failover support when a database goes down
• http://codex.wordpress.org/HyperDB

Replicated Data
DB Master
Web
Memcache
DB Slave

A Balancing Act
Load Balancer
Web 1 Web 2 Web 3

Variations on a Theme
• Master / Relay / Slave
• Slave just for backups
• Multiple data centers
• Task specific web servers

When Everything Goes
Wrong

Hire An Amazing
SysAdmin

Thank You

Find Me
• http://josephscott.org/
• joseph@josephscott.org
• http://twitter.com/josephscott/
• #wordpress-dev