How to troubleshoot WordPress performance

These are the slides from a talk given at WordCamp Halifax 2017.

Have you ever had a client come up to you and ask why a WordPress page was slow to load? We’ve all had that happen at some point or another. Especially nowadays with the increased importance of page load times! (Everything has to be fast fast fast!)

But what do you do when someone asks you to fix such an issue? It can feel like finding a needle in a haystack. The issue could be anywhere. (It really can!)

So how can you troubleshoot what’s going on? There are a lot of tools at your disposal to help you figure things out. But that doesn’t mean that you’re any closer to knowing what’s going on.

This is what this talk will help you with. We’ll look at the tools that you can use to solve this tricky issue. But we won’t stop there either We’ll also go over how to interpret what these tools are telling you. Because that’s how you’ll get to the root of the issue so that you can fix it.

You can read the companion article at: https://carlalexander.ca/troubleshoot-wordpress-performance

Transcript

1. How to troubleshoot WordPress performance
2. Carl Alexander
3. @twigpress
4. carlalexander.ca
6. Common situation
7. Client: WordPress is slow.
8. Client: Can you help?
9. You:
10. Load times are important
11. But hard to debug
12. Needle in a haystack
13. Issue can be anywhere (It really can!)
14. Lots of tools available
15. What’s a WordPress performance issue?
16. Slowness defines performance issues
17. Example: Loading a page is slow
18. Example: Site search is slow
19. Example: Publishing is slow
20. Example: “Everything is slow”
21. WordPress takes too long to do something
22. Frustrates the client
23. Has a financial impact
24. Where can you find them?
25. What happens when you request a web page?
28. Most obvious location
29. Can be your code
30. Can be plugin code
31. Can be theme code
32. Check PHP code
33. Check JavaScript code
35. Other common location
36. Dozens of queries on each page load
37. Only takes one slow query
39. Hard to diagnose
40. Hardware and Software
41. Varies from host to host
42. Why picking a good host is important
44. Hard to diagnose as well
45. Browsers are complex
46. Lots going on between requesting and rendering
47. Can appear anywhere between both points
48. Questions?
49. Browser tools
50. Web developer tools
51. Most important tool at your disposal
52. Available on all browsers
53. Mandatory tool for web development
54. Console panel
55. First panel to look at
57. Shows error messages and warnings
58. Useful for rendering performance issues
59. But mostly for JavaScript
60. Network Panel
62. Look at waterfall first
63. Scan for long bars
65. Slow first request often means issue with server
67. Time To First Byte (TTFB)
68. Time between request and start of response
69. One of the best metrics for application performance
70. Not a silver bullet
71. Don’t forget summary!
77. Web page analysis services
80. Questions?
81. Server tools
82. If nothing found in browser
83. Problem is figuring out where on the server
84. Two sources of performance issues (Hardware and Software)
85. Start with WordPress
86. Query Monitor
87. Best debugging plugin for WordPress
88. Collects all sorts of information on WordPress (More than just SQL queries!)
89. Visible from the admin bar
90. Visible from the admin bar
91. Visible from the admin bar
92. Visible from the admin bar
93. Additional HTTP requests can also slow things down
97. Database server processes
100. SQL query: SHOW FULL PROCESSLIST;
101. Additional tools (But need access to your server)
102. Slow logs
103. MySQL tuner
104. Application performance monitoring
105. Questions?
106. Recapping
107. How do you use these tools together?
112. Still stuck? Ask for help!
113. Questions?
114. Thank you!