PEG.js based parser introduced a performance regression #1646
Description
After updating the plugin on a site I noticed a performance decrease by 2-3 seconds.
$ wp profile stage --fields=stage,time,cache_ratio
+------------+---------+-------------+
| stage | time | cache_ratio |
+------------+---------+-------------+
| bootstrap | 1.0175s | 88.3% |
| main_query | 0.025s | 90.74% |
| template | 4.3431s | 93.54% |
+------------+---------+-------------+
| total (3) | 5.3856s | 90.86% |
+------------+---------+-------------+
vs.
$ wp profile stage --fields=stage,time,cache_ratio --skip-plugins=gutenberg
+------------+---------+-------------+
| stage | time | cache_ratio |
+------------+---------+-------------+
| bootstrap | 1.0935s | 88.09% |
| main_query | 0.0206s | 90.74% |
| template | 0.3426s | 93.54% |
+------------+---------+-------------+
| total (3) | 1.4567s | 90.79% |
+------------+---------+-------------+
Checking further
wp profile stage template --fields=hook,time,cache_ratio
+--------------------------+---------+-------------+
| hook | time | cache_ratio |
+--------------------------+---------+-------------+
| template_redirect:before | 0.001s | |
| template_redirect | 0.0239s | 98.46% |
| template_include:before | 0.0008s | 100% |
| template_include | 0s | |
| wp_head:before | 0.0028s | 100% |
| wp_head | 0.0904s | 98.31% |
| loop_start:before | 0.0287s | 93.58% |
| loop_start | 0s | |
| loop_end:before | 3.1046s | 91.02% |
| loop_end | 0s | |
| wp_footer:before | 0.0607s | 92.7% |
| wp_footer | 0.0017s | 100% |
| wp_footer:after | 0.0002s | |
+--------------------------+---------+-------------+
| total (13) | 3.315s | 96.76% |
+--------------------------+---------+-------------+
So I removed the filter on the_content and the load was back to normal. I also reverted the do_blocks() function to the previous version and the load was still normal. But once the PEG version is in use the page load increases by ~3 seconds.
Will investigate further to get the exact cause for this.