Slow CSS/JS processing

Hi,

I’ve recently had a pleasure working on LiteSpeed server and finally got a chance to test your plugin. And! just yesterday you released version for non-LiteSpeed servers (whaaaat?), so I’ve compared test results.

And I have one question about minify and combine option. Should it slow down website so much during first load and why it’s still slower to load cached files when comparing different plugins?

All my results are based on pingdom test from Sweden location.

LiteSpeed SSD server, HTTP/2, SSL —————

Because it’s http/2 I’ve minified both css and js files but combined only js (http/2 still got some limits)

For example, this is an average “wait” time for css/js files on my LiteSpeed server after Purge All action https://monosnap.com/file/hLK9xRaKv3Lj26qyeojL3zORpceoZg
For second run it’s <200ms

During that test I’ve encountered probably a bug. When theme was including style.css with only theme comment data like, theme name, author and so on, after minifying the file was empty. That caused this resource to be processed over and over again which was slowing down whole website. https://monosnap.com/file/zbjUSJA9ZMxVUOd4J1MBgT8qXNtr5S Loading “wait time” of that resource (empty css file) took almost 2s on each refresh. So I’ve excluded this file from processing and tested again. Btw, this isn’t uncommon for theme developers to create empty style.css file for WP with only a comment. Not sure why they enqueue it in wp_enqueue_style, but it happens.

After clearing cache website loaded in 13.92 s, and wait time for css/js resources was between 5-10s
Second run was around 1s to load, and wait time for css/js 120 – 160 ms

I’ve compared this with WP Fastest Cache and Minify+Combine+Refresh
First run loading time was 4.04 s, document wait time was 3.2 s, and resources wait time was 45-130 ms
second run website loaded in 1.13 s, document wait 85ms, css/js wait time 44-130 ms

So cached result is somewhat comparable, yet during cache creation loading time was waaaay longer with LiteSpeed Cache.

For second website also on LiteSpeed server first run was 7.7s (this site have less resources than first one) with wait time 3-4.8s for css/js, and <1s with second run. css/js wait time ~120ms

If I disable css minify/combine part for resources then after cache clear the loading time is 1.38s

Non LiteSpeed SSD server, HTTP/1, SSL ———————

Then I’ve tested third website with new update, not a LiteSpeed server and without HTTP/2 so this will is a bit different, but the timings for processing css/js files is still very long and are long even after creating cache files.

Setting to minify but not combine:
First run wait time for css is 1.5-3.5s
Second run wait time is still long, 0.6-1.2s even tho it should load static files (they are created I’ve checked)
Document wait time is between 1.1s-1.3s for both tests

Because on that server theres no support for http/2 I’ve turned on combine part.

First run, document wait time increased to 2.8s comparing to combine OFF setting, and css/js wait time was 1s.
Second run, document wait time 1.3s, css 850ms, js 1.4s
Third run (just in case), document 1.8s, css 773ms, js 2.69s wait time.

So it looks like, even though files are created, they are not served as static resources. Not sure if in this case it’s because it’s new release not fully tested with non litespeed servers, but overall processing CSS/JS files via LiteSpeed plugin takes very long time. In theory css/js files won’t change that often, but still. That’s a lot of time imo.

Switching back to Fast Velocity Minify
First run, document wait time 3.9s, css and js wait time ~ 40ms
Second run, document wait 1.1s, css/js ~ 60ms
third run, document 1.05s, css/js ~55 ms

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Overall the caching part on LiteSpeed server in my tests is great. The minify combine part not so much. I was hoping to use one plugin for website optimizations, but so far it looks like we need to still use different plugins for caching and css/js processing.

So returning to my question. Is this LiteSpeed plugin, or server configuration. Comparing with other plugins, it looks more like plugin issue. Is this something that can be improved in the future?