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WordPress + performance

Vladimir Smitkavladimir.smitka@lynt.cz

@smitkaLynt 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?

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

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

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

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

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 + JetpackRequests per second: 2.94 [#/sec] Time per request: 1360.454 [ms]

Congrats, we were able to degrade

performance more than 5 times in few

minutes!

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Motivation: our webserver

• WP + some common pluginsRequests per second: 319.26 [#/sec]Time per request: 12.529 [ms]Ping 2,5 ms

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

List of all queries

Queries by function

Queries by component

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Query Monitor – more info

HTTP requests based on wp_remote_X functioncurl, file_get_contents etc. are not captured [you can capture them by traffic analysis (tcpdump, wireshark)]

Some important constants are missinge.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 infrastructure3 parts – HTTP server, DB server a StorageEach with different requirements…

DB

Storage

WEBLOADBALANCER

Cloud

× 2

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Monitoring – looking for bottle neckhtop

Munin

http://munin-monitoring.org/http://www.zabbix.com/http://www.librenms.org/

htopiotopiftopnmon

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PHP versions

• OpCode cache• Object cache

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

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

Apache Apache - .htaccess

Nginx0

2

4

6

8

10

12

Apache vs Nginx

req/

s

Apache Apache - .htaccess

Nginx Nginx + Microcache

0

50

100

150

200

250

300

Apache vs Nginx + Microcache (unfair comparism)

req/

s

AllowOverride None

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/wp-content/uploads/revslider/classicslider/bike.jpg

Hey, is .htacces

s 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!“

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 requestsanalysis, 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?

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

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!

OMG!

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Another problem – with fix!

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/5311858 xdebug.remote_enable = 1

xdebug.profiler_enable_trigger = 1xdebug.trace_format = 1xdebug.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

linespent time

Difference of consumed memory

Memory consuption during script execution

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Tracing part of codexdebug_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 2230882 3 0 0.005621 223128 rand 0 D:\htdocs\wp4\info.php 72 3 1 0.005740 2231282 4 0 0.005770 223128 rand 0 D:\htdocs\wp4\info.php 72 4 1 0.005879 2231282 5 0 0.005908 223128 rand 0 D:\htdocs\wp4\info.php 72 5 1 0.006016 2231282 6 0 0.006044 223096 xdebug_stop_trace 0 D:\htdocs\wp4\info.php 9 0.006130 223120TRACE END [2015-10-01 11:49:49]

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Stepping through codeDefault: localhost:9000

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Père Fouras: Pensée du jour

„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.

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