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http://lynt.cz
WordPress + performance
Vladimir Smitka
vladimir.smitka@lynt.cz
@smitka
Lynt services s.r.o.
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Hidden advertisement
• We launched a new blog about
automatization in PPC few days ago
http://ppc-scripts.eu
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How to speedup WP?
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Let someone else do it!

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

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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!
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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
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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
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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…">
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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/
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Autoptimize
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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/
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WP Super Cache
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Thank you for your attention!

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

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Resources loading under hood
• http://www.webpagetest.org/
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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
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Keep Alive
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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?

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HTTPS & SPDY & HTTP/2
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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.

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What slows TTFB down
• MySQL queries
• Unusage of cache
• HTTP requests (e.g. update checks)
• More plugins = more requests
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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
Requests per second: 4.61 [#/sec]
Time per request: 868.450 [ms]
• WP + SliderRevolution + CF7 + Yoast SEO + WPML + Jetpack
Requests per second: 2.94 [#/sec]
Time per request: 1360.454 [ms]
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Congrats, we were
able to degrade
performance more
than 5 times in few
minutes!

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Motivation: our webserver
• WP + some common plugins
Requests per second: 319.26 [#/sec]
Time per request: 12.529 [ms]
Ping 2,5 ms
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35 ms
Dirty caching tricks are used, of course. We will talk about it later.

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P3 Profiler
• https://wordpress.org/plugins/p3-profiler/
• The simplest, provides less information, bad accuracy
• It can help detect a problematic plugin
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Query monitor
• https://wordpress.org/plugins/query-
monitor/
• Detailed overview what happens
in WP
• Great helper during development
(e.g. shows active conditions)
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Query Monitor – DB queries
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List of all
queries
Queries by
function
Queries by
component

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Query Monitor – more info
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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

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Looking from the other side
• We have examined website from application
look
• Now it is time to look where apps are running
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Server infrastructure
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3 parts – HTTP server, DB server a Storage
Each with different requirements…
DB
Storage
WEBLOADBALANCER
Cloud
× 2

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

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

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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)
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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
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71 of them is Slider Revolution

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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
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HTTP server
• Many options to run PHP
• Apache (prefork) + mod_php
• Apache (mpm event/worker) + PHP-FPM, FastCGI
• Nginx + PHP-FPM
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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

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

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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
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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!“
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Very good
result with
cheap VPS

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The real tools
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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)
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Performance
consumed by
function itself

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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/
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The big grey bar

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Why is do_action so slow?
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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).

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Big problem - demo
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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

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Another problem – with fix!
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OMG!

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

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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
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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
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xdebug.remote_enable = 1
xdebug.profiler_enable_trigger = 1
xdebug.trace_format = 1
xdebug.trace_enable_trigger = 1

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

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Tracing part of code
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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 0 0.005770 223128 rand 0 D:htdocswp4info.php 7
2 4 1 0.005879 223128
2 5 0 0.005908 223128 rand 0 D:htdocswp4info.php 7
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]

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Stepping through code
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Default: localhost:9000

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

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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)
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This is the end, folks.
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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