How to test apache.

Create 2 files:
testload.php
test.php

Create a php file testload.php that checks the existence of another file named test.php in the same directory of two CentOS 7 servers with the same hardware characteristics and load but with different MPM. One of them will use event and the other one will use prefork.

<!--?php $filename = 'test.php'; if (file_exists($filename)) { echo "The file $filename exists"; } else { echo "The file $filename does not exist"; } ?-->

With ab, we will sent 50 (-c 50) concurrent requests at the same time and repeat the test 1000000 times

# ab -c 50 -n 100000 http://localhost/testload.php

200 simultaneous requests until 2000 requests are completed:

# ab -k -c 100 -n 2000 localhost/testload.php

Another test to localhost
PREFORK

]# ab -c 50 -n 100000 http://localhost/index.html
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient)
Completed 10000 requests
Completed 20000 requests
Completed 30000 requests
^C

Server Software:        Apache/2.4.6
Server Hostname:        localhost
Server Port:            80

Document Path:          /index.html
Document Length:        15167 bytes

Concurrency Level:      50
Time taken for tests:   3596.808 seconds
Complete requests:      34570
Failed requests:        0
Write errors:           0
Non-2xx responses:      34571
Total transferred:      537122767 bytes
HTML transferred:       524331497 bytes
Requests per second:    9.61 [#/sec] (mean)
Time per request:       5202.210 [ms] (mean)
Time per request:       104.044 [ms] (mean, across all concurrent requests)
Transfer rate:          145.83 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       3
Processing:   213 5198 241.5   5203   10154
Waiting:      174 4428 227.6   4435    9302
Total:        214 5198 241.5   5203   10154

Percentage of the requests served within a certain time (ms)
  50%   5203
  66%   5264
  75%   5302
  80%   5327
  90%   5391
  95%   5449
  98%   5532
  99%   5617
 100%  10154 (longest request)