Still trying to track down the slowness. Watching top tells me that most of the time for a request is spend by PHP-FPM. Will be trying

“Pay special attention to the slowlog settings (request_slowlog_timeout and slowlog directives), that is, through this log and a reasonable amount of timeout, you can easily see which php calls from your application take longer than expected and start debugging them right away.” — https://cwiki.apache.org/confluence/display/HTTPD/PHP-FPM [apache org]

... to try and see what’s going on. !fnetworks