How to cope with the error [pool www] seems busy?

Help set up PHP-FPM.

My config / Server Configuration:

Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz Core: 9 Ram: 10GB Swap: 2GB 

When reaching 200 online for a laravel project, PHP-FPM throws a 502 error. Here's what PHP-FPM writes in logs. / When reaching 200 online on the project, PHP-fpm cuts off. (About 10-15 seconds)

 WARNING: [pool www] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 32 children, there are 16 idle, and 186 total children 

My last config pool.d / Last config

 pm = ondemand pm.max_children = 400 pm.process_idle_timeout = 5s; pm.max_requests = 0 

1 PHP-fpm process takes 50mb on average. In the old PHP-fpm config was such an error.

 WARNING: [pool www] server reached max_children setting (100), consider raising it