Hi,
we’re running FreePBX 11 for several years now, but over the last few months we’re seeing growing spikes of CPU load coming from MySQLd, that recently started reaching 100%, and that I failed to get analyzed yet, so I hope for some support from here 
The spike occurs every 3 minutes, and takes about 1.5 minutes.
‘show full processlist’ in mysql tells me that the query is “UPDATE qxact_agent_actions, users SET qxact_agent_actions.agent = users.name WHERE (qxact_agent_actions.agent = users.extension) AND time >= $2_hours_ago”.
For some odd reason, this query ties up one core for more than a minute.
Running the same query from the mysql CLI manually comes back instantly.
The ‘qxact_agent_actions’ table when inspected comes up as completely empty, and the ‘users’ table is tiny, with our roughly 200 call center agents in there.
I have run the usual analyze/optimize/reindex table commands, but no change was noticeable, which makes me assume that the CPU load is actually coming from some spinlock or other tied up situation.
I’ve grepped through the FreePBX sources, but I couldn’t find any place where this query is actually generated… the above table name comes up only once in the installer.php.
As the load spike occurs exactly every 3 minutes, I guess it’s some kind of scheduled task… but nothing comes up in cron that would fit the bill.
Please share your insights if you have intimate knowledge of FreePBX’s database tasks 
Regards
~Woo