nginx-large concurrent stress test data, seeking great God guidance

nginxphp concurrency

First of all, thank you!

Intuitive point-in-line test data
The test data is as follows
Webbench 5000 Concurrent 60-second access to TXT file

Webbench 30000 Concurrent 60-second access to TXT file

Webbench 2000 Concurrent 60-second access to PHP files only wrote a phpinfo ()

Webbench 10000 Concurrent 60-second access to PHP files only wrote a phpinfo ()

Webbench 10000 concurrent 60 second top results

Test environment
CPU16 Kernel Memory 64G
System CentOS-6.5 64-bit
nginx/1.0.13
php5.6.7

The following question asks the big God to instruct
1. Regardless of the performance of the program, in this system, whether there is more space for optimization, the limit can reach what extent, how to adjust?
2. When the 10000 concurrent access to PHP, the server load is not very high, SSD drive no raid, where is the bottleneck?

Some configuration parameters are attached below
Php-fpm.conf

Sysctl.conf

Nginx.conf

