Page generation time takes more time after a while not using the site.

Unfortunately disk I/O is one of the things that QM doesn’t track as I’ve found no reliable way to do this at the PHP layer.

Is there anything shown on the Transients panel in QM when this happens? If so take a look at the functions shown to see if there’s any unexpected data processing happening.

Something may be performing an HTTP request directly with Curl instead of via the WordPress HTTP API. This is impossible for QM to detect because PHP doesn’t expose the Curl handle nor provide an event system to hook into for monitoring purposes. You’ll need to search your codebase for functions such as curl_init and investigate.

I notice there are no cache hit and miss stats for your object cache. These are usually shown in the Cache section in the Overview. This might mean you’re using an uncommon cache driver which doesn’t expose its stats. The hit and miss ratio isn’t especially useful on its own but it can be indicative of a problem.

Best of luck.

I set “WP_HTTP_BLOCK_EXTERNAL” is true in wp-config.php so it supposes to block all HTTP API including those HTTP request directly with Curl, isn’t it?

I also find it weird that when I disable object cache in w3 cache plugin. There are cache hit and miss stats info in the Cache section. And when I enable it, there are no information in cache section.

However, if I enable object cache I can see the select query drop to only 110 in Database Queries section and it shows 395 when object cache is disabled.

The below image is when object cache is disabled.