WordPress performance tuning

http://lynt.cz
WordPress + performance
Vladimir Smitka
vladimir.smitka@lynt.cz
@smitka
Lynt services s.r.o.
9. 10. 2015 1

Hidden advertisement
• We launched a new blog about
automatization in PPC few days ago
http://ppc-scripts.eu
9. 10. 2015 2

How to speedup WP?
9. 10. 2015 3
Let someone else do it!

Thank you for your
attention!
9. 10. 2015 4

Speech no. 2 – DIY
• What mentioned services do?
– Caching of generated page on their servers
– Resources optimization – combine&minify JS & CSS, image
optimization
9. 10. 2015 5
http://lynt.cz/blog/wordpress-
in-the-czech-complex-research

Image optimization
• Appropriate dimensions
• Check if thumbnails are really small
• Use appropriate formats
• „Web graphics“ – 8 bit PNG, SVG
• Photos – JPG (quality 75 is OK, 60 in
Photoshop)
• Videos – MP4, FLV, GIF!
9. 10. 2015 6

Image optimization – 24 bit PNG
• Usually used because of alpha channel
• They are often used unnecessarily – alpha
channel is also supported by 8 bit PNG (produced
images are much smaller), Photoshop couldn‘t
produce it recently (new Photoshop CC can)
• https://tinypng.com/
• TruePNG - http://css-ig.net/articles/truepng
• AdvDef -http://advancemame.sourceforge.net/comp-
download.html
9. 10. 2015 7

Image optimization - plugins
• https://wordpress.org/plugins/ewww-image-
optimizer/ + https://ewww.io
• https://wordpress.org/plugins/shortpixel-
image-optimiser/ - 100 images/month for
free
• https://wordpress.org/plugins/kraken-image-
optimizer/ - subscription
9. 10. 2015 8

CSS sprites & data URI
• What is the problem?
• HTTP headers are 0.5 - 1KB length in average (in case of
small images headers are bigger than useful data)
• Connection time to the server is negligible
• Our goal is to reduce number of requests to the server:
A) If you have more images you can merge them to one bigger
image (http://draeton.github.io/stitches/)
B) You can load particular small images with data URI:
<img src="data:image/png;base64,…data v
base64…">
9. 10. 2015 9

JS & CSS optimization
• Goal – reduction of requests to server,
reduction of size (again)
• You can combine more CSS and JS files into
one + minify them
• https://wordpress.org/plugins/autoptimize/
• https://wordpress.org/plugins/bwp-minify/
9. 10. 2015 10

Autoptimize
9. 10. 2015 11

Page cache
• Saves processed page into static HTML file for
future load
• https://wordpress.org/plugins/wp-super-
cache/
• https://wordpress.org/plugins/w3-total-
cache/
9. 10. 2015 12

WP Super Cache
9. 10. 2015 13

http://lynt.cz9. 10. 2015 14
Thank you for your attention!

Speech no. 3 – the real one
9. 10. 2015 15
Problem diagnostics:
https://gtmetrix.com/
Application Resources

Resources loading under hood
• http://www.webpagetest.org/
9. 10. 2015 17

Resources loading – common problems
• Expires headers (mod_expires) – ensure that
resources don‘t need to be downloaded again
(else browser will use heuristic analysis)
• GZIP compression (mod_deflate) – usually saves
about 30-70% size of text files
• Keep Alive – keeps connections open, there is no
need to establish connection again, it uses little
more RAM
9. 10. 2015 18

Keep Alive
9. 10. 2015 19
30ms
Keep Alive turning off may be
critical on sites with many
resources - especially on mobile
devices with long latency
Ping 300ms, 150 resources, 5 simultaneous connections:
2x300x150/5 = 18s waiting for connection + ending
Why so many
redirects?

HTTPS & SPDY & HTTP/2
9. 10. 2015 20
HTTP/2
• encrypt,
• compress,
• keep alive,
• binary protocol
Neither combining CSS and JS,
nor using sprites is necessary.
Using these techniques may
little slow down your site with
HTTP/2.
Reconnecting isn‘t a problem –
only required resources are
downloaded.

What slows TTFB down
• MySQL queries
• Unusage of cache
• HTTP requests (e.g. update checks)
• More plugins = more requests
9. 10. 2015 21

Effect of plugins
• Test on VPS from WEDOS (1 core, 4G RAM)
ab -n 1000 -c 4 http://domain
• Clean WP:
Requests per second: 15.93 [#/sec]
Time per request: 251.095 [ms]
• WP + SliderRevolution + CF7 + Yoast SEO
• WP + SliderRevolution + CF7 + Yoast SEO + WPML + Jetpack
9. 10. 2015 22
Congrats, we were
able to degrade
performance more
than 5 times in few
minutes!

Motivation: our webserver
• WP + some common plugins
Ping 2,5 ms
9. 10. 2015 23
35 ms
Dirty caching tricks are used, of course. We will talk about it later.

P3 Profiler
• https://wordpress.org/plugins/p3-profiler/
• The simplest, provides less information, bad accuracy
• It can help detect a problematic plugin
9. 10. 2015 24

Query monitor
• https://wordpress.org/plugins/query-
monitor/
• Detailed overview what happens
in WP
• Great helper during development
(e.g. shows active conditions)
9. 10. 2015 25

Query Monitor – DB queries
9. 10. 2015 26
List of all
queries
Queries by
function
Queries by
component

Query Monitor – more info
9. 10. 2015 27
HTTP requests based on wp_remote_X function
curl, file_get_contents etc. are not captured [you can capture them by traffic analysis (tcpdump, wireshark)]
Some important constants are missing
e.g. SAVEQUERIES – another IO req.
Writes into file:
IO operations
Minified libraries
won‘t be used:
more data
HTTP requests

Looking from the other side
• We have examined website from application
look
• Now it is time to look where apps are running
9. 10. 2015 28

Server infrastructure
9. 10. 2015 29
3 parts – HTTP server, DB server a Storage
Each with different requirements…
DB
Storage
WEBLOADBALANCER
Cloud
× 2

Monitoring – looking for bottle neck
9. 10. 2015 30
htop
Munin
http://munin-monitoring.org/
http://www.zabbix.com/
http://www.librenms.org/
htop
iotop
iftop
nmon

PHP versions
• OpCode cache
• Object cache
9. 10. 2015 31
Newer PHP versions
are faster and can
use OpCache more
effectively (it costs
more RAM)
PHP version performance – Apache Benchmark/WP

OpCode cache
• PHP language is compiled to Bytecode during
every request
• OpCache saves result for future use, there is no
need of recompilation
• You need install it (PHP < 5.5)
• APC
• Xcache
• Zend OpCache (part of PHP 5.5)
9. 10. 2015 32

Object Cache
• Usually part of OpCache module + standalone
• User can save data into it for future use
• You need to enable it and allocate storage
• You need to install object backend drop-in into WP
– APC
– Xcache
– APCu (for usage with Zend OpCache)
– Redis
– Memcached
• WP will use it for transient variables etc. – it can reduce
DB queries rapidly
9. 10. 2015 33
71 of them is Slider Revolution

Some points from Query Monitor
• You'll probably find that menu and some widgets
don‘t use cache
• http://afterburner.voceplatforms.com/back-
end.html#voce-widget-cache
• http://afterburner.voceplatforms.com/back-
end.html#voce-cached-nav
• There are many more tips and tools on this website
9. 10. 2015 34

HTTP server
• Many options to run PHP
• Apache (prefork) + mod_php
• Apache (mpm event/worker) + PHP-FPM, FastCGI
• Nginx + PHP-FPM
9. 10. 2015 35
Apache
Apache -
.htaccess
Nginx
req/s 8.2 9.35 9.96
0
2
4
6
8
10
12
req/s
Apache vs Nginx
Apache
Apache -
.htaccess
Nginx
Nginx +
Microcache
req/s 8.2 9.35 9.96 279.97
0
50
100
150
200
250
300
req/s
Apache vs Nginx + Microcache
(unfair comparism)
AllowOverride None

/wp-content/uploads/revslider/classicslider/bike.jpg
9. 10. 2015 36
Hey, is
.htaccess
here?
And
here?Here?
Or
here?
Here it is!
Apache is not convenient to server static files

Back to our webserver
• We used microcache to achieve excellent results –
Nginx will remember result of request for a while
(seconds, minutes)
• This technic is useful in case of peak traffic – e.g after
new content release
• Microcache: Requests per second: 319.26 [#/sec]
• WP Supercache: Requests per second: 270.84 [#/sec]
• No caching *: Requests per second: 13.52 [#/sec]
* Test was performed with hundreds other requests on production environment
9. 10. 2015 37

The last benchmark
• Test to the WEDOS VPS with more concurrency
ab -n 1000 -c 40 http://domain
• Requests per second: 1191.49 [#/sec] (mean)
• Time per request: 33.572 [ms] (mean)
• Time per request: 0.839 [ms] (mean, across all
concurrent requests)
Important note:
„Using cache isn‘t so easy, you need to resolver cache invalidation!“
9. 10. 2015 38
Very good
result with
cheap VPS

The real tools
9. 10. 2015 39

Blackfire.io
• Performance profiling, great visualization
• Requires to install agent and PHP extension - tutorial
• You can run profiling from Chrome with Blackfire
Companion
• Hack version for free
• Premium version 82,5€/month
(DB queries and HTTP requests
analysis, teams,
longer data retention)
9. 10. 2015 40

Performance
consumed by
function itself

Localization takes more than 30%?
• WP uses slow PHP implemetation of GetText
• Solution:
• https://github.com/LyntServices/WP-lang-
cache (my very old hack to WP core, I have
more modifications to use ObjectCache)
• https://wordpress.org/plugins/mo-cache/
9. 10. 2015 42

The big grey bar

Why is do_action so slow?
9. 10. 2015 44
From PHP5.6 you can use optimized Argument Unpacking functionality:
…$the_['acceped_args']
Call_user_func_array function itself isn‘t problem – problem is hundreds and
thousands calls of this function (or any other function).

Big problem - demo
9. 10. 2015 45
Recursion – shortcodes
in shortcodes in
shorcodes …
Huh, so
many calls!
Big grey bar – use of object
cache makes it worse – it
will call many userializations

Another problem – with fix!
9. 10. 2015 46
OMG!

Another problem – with fix!
9. 10. 2015 47
Fix:
extension=json.so
Native JSON extension was missing!
9.2s => 0.0248s = 370x better performance with one line 

Dead end of profiling
• When you profile WP in Blackfire you usually
stop in two cases:
1) do_action – common and heavy used WP
function (like apply_filters), you cannot track
cause and effect of particular call in Blackfire
2) Grey bar – performance is lost inside function –
code isn‘t visible
• Now debugging is come
9. 10. 2015 48

Xdebug
• PHP extension: http://xdebug.org/
• Wizard helps you to download the correct
versions and what to insert into PHP config
according your phpinfo() output:
http://xdebug.org/wizard.php
• Great config setting explanation:
https://gist.github.com/IngmarBoddington/53
11858
9. 10. 2015 49
xdebug.remote_enable = 1
xdebug.profiler_enable_trigger = 1
xdebug.trace_format = 1
xdebug.trace_enable_trigger = 1

Xdebug – what to do?
• Allows to go through code step by step from IDE
• Trace-log generation
• Code coverage analysis
• Profiling (more overhead than Blackfire)
xdebug.profiler_enable_trigger = 1
?XDEBUG_PROFILE
• You can use WebGrind for visualization:
https://github.com/jokkedk/webgrind
• Xdebug Helper – Chrome extension:
https://chrome.google.com/webstore/detail/xdebug-
helper/eadndfjplgieldjbigjakmdgkmoaaaoc
9. 10. 2015 50

WebGrind
9. 10. 2015 51

Trace
• Tracelog – huge amount of data
• Useful for resolving memory problems
• https://github.com/corretge/xdebug-trace-gui
9. 10. 2015 52
line
spent time
Difference of
consumed memory
Memory consuption during script execution

Tracing part of code
9. 10. 2015 53
xdebug_start_trace('for.xt');
for ($i=0;$i<3;$i++){
echo rand(0,$i);
}
xdebug_stop_trace();
TRACE START [2015-10-01 11:49:49]
2 2 1 0.005554 223088
2 3 0 0.005621 223128 rand 0 D:htdocswp4info.php 7
2 3 1 0.005740 223128
2 4 1 0.005879 223128
2 5 1 0.006016 223128
2 6 0 0.006044 223096 xdebug_stop_trace 0 D:htdocswp4info.php 9
0.006130 223120
TRACE END [2015-10-01 11:49:49]

Stepping through code
9. 10. 2015 54
Default: localhost:9000

Père Fouras: Pensée du jour
9. 10. 2015 55
„This is the end of web developers era,
era of system adminstrators has begun.“

Summary – performance analysis
• How it shows from outside?
– https://gtmetrix.com/
– http://www.webpagetest.org/
– Developer console in browser
• What slows WP down?
– P3 profiler – tentative detection of slow plugins
– Query monitor – particular DB queries and more
• Profiling and debugging
– Blackfire.io
– Xdebug (visialization with webgrind)
9. 10. 2015 56

This is the end, folks.
9. 10. 2015 57
Small gift: Blackfire.io Premium for a month:
DODWEDOS102015
valid until 19.10.2015
You can use this coupon during monthly subscription checkout
You can follow me on twitter @smitka and visit our blog http://lynt.cz/blog

WordPress performance tuning

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