Every change to a blog post on this website took a whopping 20 second delay before I could see the result.

The solution was really simple, really. And was committed in the README as a TODO over 3 years ago.

Upgrade Jekyll

Upgrading Jekyll from v3.9.0 to 4.2.2 already brought the reload time down from 20s to 12s.

After updating the Gemfile, I also had to upgrade a few other gems:

gem "jekyll", "4.2.2"

group :jekyll_plugins do
  gem "kramdown-parser-gfm"
  gem "jekyll-feed", "~> 0.17"
  gem "jekyll-paginate", "~> 1.1.0"
  gem "jemoji", "~> 0.13.0"
  gem "jekyll-gist", "~> 1.5.0"
  gem "jekyll-avatar", "~> 0.8.0"
  gem "jekyll-redirect-from"
end

And then apply the changes with bundle update.

There probably isn’t much you have to do when upgrading from v3 to v4.

• ruby -v needs to be >=2.7.0
• {{ site.baseurl }}/{% post_url some-post %} -> {% post_url some-post %}

Incremental Serving

The next logical step is to only re-render what has actually changed. This reduced reload times from 12s to 3s 🎉🥳

bundle exec jekyll serve --incremental

# or:
bundle exec jekyll serve -I

Caveat

The --incremental will only update file(s) that have actually changed. This means that a new post will not appear in your blog post listing / home page because that file has not changed…

To force an update:

touch blog/index.html

Which works on my Windows system because of this function:

function touch($file) {
	if (Test-Path $file) {
		(Get-ChildItem $file).LastWriteTime = Get-Date
	} else {
		$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding $False
		$path = Get-Location
		$path = Join-Path -Path $path -ChildPath $file
		[System.IO.File]::WriteAllText($path, "", $Utf8NoBomEncoding)
	}
}

For pages like that, you can automate this by adding to the front matter:

regenerate: true

Windows Directory Monitor

Maher4Ever/wdm : A threaded directories monitor for Windows.

For Windows, you also need to add wdm to the Gemfile:

# Performance-booster for watching directories on Windows
gem "wdm", "~> 0.2.0", :platforms => [:mingw, :x64_mingw, :mswin]

bundle install and you’re ready to go!

Development config.yml

This can be improved even further by not doing some plugin work that is typically not necessary during development anyway.

bundle exec jekyll serve --incremental --config _config_dev.yml

In the copied _config_dev.yml I removed all the gems in group :jekyll_plugins do.

This however only reduced the reload time by 0.5s which wasn’t worth it for me as I’d have to keep two config.ymls in sync.

Limit Posts

In the _config_dev.yml, you can specify to only render the last x posts. This turned out to be not very useful because the profiler told me that most time is spent on reading and not so much on the rendering phase.

# While this seems like a super great idea, this no longer makes
# it possible to use post_url to point to a post that is older..
limit_posts: 20

Profiling

If it’s still taking too long, you can use --profile to figure out what’s going on.

bundle exec jekyll serve --profile

PowerShell Profile

I have these added to my ps profile, because who wants to remember/write all the bundle exec etc etc 😀

function Start-Jekyll {
	bundle exec jekyll serve --incremental
}
function Start-JekyllWithDrafts {
	bundle exec jekyll serve --drafts --incremental
}
function Start-JekyllDev {
	bundle exec jekyll serve --incremental --config _config_dev.yml
}
function Start-JekyllDevWithDrafts {
	bundle exec jekyll serve --drafts --incremental --config _config_dev.yml
}

Set-Alias bejs Start-Jekyll
Set-Alias bejsd Start-JekyllWithDrafts
Set-Alias bejsdev Start-JekyllDev
Set-Alias bejsddev Start-JekyllDevWithDrafts