performance – Horrendously slow admin and pretty slow sites
We host dozens of plain PHP sites that respond within milliseconds. The average page load time is around 10 ms. One of our users installed 2x WP 5.5 sites and gradually upgraded them to 6.0. Their page load times are 5 seconds and up, and it is slowing down their admin users.
The sites run on a FreeBSD 13.1 VM, on a WS 2012 host. The hardware is 2x 2nd gen Xeon 3 GHz, 16 physical cores total, off an SSD. There is plenty of free RAM, both on the VM and on the host.
We suggested they install XML-RPC plugin and disable heartbeat and other resource-hungry items. It did not help at all. We looked at all of the top solutions on Google to “wordpress admin slow” but none helped make any difference whatsoever.
We tried to temporarily put their sites on the Apache that runs directly on the host OS, but it made matters ever so slightly worse (by a factor of 10%) across both the admin and the actual sites.
When an admin page (dashboard, plugins, media, posts – does not matter which) is requested, WordPress seems to be taking its time w/o any signs of resource utilization. It simply sits for 5+ seconds, w/o CPU load or disk activity, and then the CPU load spikes and there is a disk access, for a split second, and the page loads. It happens equally with a vanilla WordPress as well as with their full sets of plugins that include WooCommerce and a tiny handful of others. Any theme.
Please help understand why WordPress is taking so much time, to load trivial pages.