Torture testing Litespeed Inbuilt cache against vB 3.8.6 PL1 front index.php page with apachebench at:
- 5000 concurrency level + 1 million requests (virtualized server allocated 1GB memory) - cache timeout was set at 120 seconds but test run lasted 127.45 seconds, so the tail end caught some php load. PHP averaged around 10MB per process.
- 5000 concurrency level + 1.5 million requests (virtualized server allocated 2GB memory) - cache timeout was set at 480 seconds while test ran only for 163.91 seconds, so well within cache timeout so no PHP usage.
Try the above with apache and only 1-2GB memory 
Not a single failed request !
5000 concurrency + 1 million requests
Apachebench = 7,846.05 rps - over 240x times apache's performance handling 100x times the number of requests and 25x times the concurrency
Code:
ab -k -n 1000000 -c 5000 http://192.168.56.101/index.php
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.56.101 (be patient)
Completed 100000 requests
Completed 200000 requests
Completed 300000 requests
Completed 400000 requests
Completed 500000 requests
Completed 600000 requests
Completed 700000 requests
Completed 800000 requests
Completed 900000 requests
Finished 1000000 requests
Server Software: LiteSpeed
Server Hostname: 192.168.56.101
Server Port: 80
Document Path: /index.php
Document Length: 19841 bytes
Concurrency Level: 5000
Time taken for tests: 127.452598 seconds
Complete requests: 1000000
Failed requests: 0
Write errors: 0
Keep-Alive requests: 418171
Total transferred: 20142500003 bytes
HTML transferred: 19874423323 bytes
Requests per second: 7846.05 [#/sec] (mean)
Time per request: 637.263 [ms] (mean)
Time per request: 0.127 [ms] (mean, across all concurrent requests)
Transfer rate: 154335.11 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 48 66.1 22 800
Processing: 89 571 694.6 567 21904
Waiting: 10 208 680.4 171 21283
Total: 109 619 702.5 618 21904
Percentage of the requests served within a certain time (ms)
50% 618
66% 665
75% 690
80% 705
90% 756
95% 871
98% 1066
99% 1191
100% 21904 (longest request)
CPU Load
Code:
top - 16:27:02 up 23 min, 3 users, load average: 9.43, 3.15, 1.56
Tasks: 136 total, 2 running, 134 sleeping, 0 stopped, 0 zombie
Cpu(s): 29.8%us, 15.0%sy, 5.0%ni, 19.3%id, 29.2%wa, 0.3%hi, 1.3%si, 0.0%st
Mem: 1026824k total, 1015532k used, 11292k free, 444k buffers
Swap: 2064376k total, 667332k used, 1397044k free, 30628k cached
5000 concurrency + 1.5 million requests
Apachebench = 9,151.34 rps - 280x times apache's performance with 150x times number of requests and 25x times the concurrency.
Code:
ab -k -n 1500000 -c 5000 http://192.168.56.101/index.php
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.56.101 (be patient)
Completed 150000 requests
Completed 300000 requests
Completed 450000 requests
Completed 600000 requests
Completed 750000 requests
Completed 900000 requests
Completed 1050000 requests
Completed 1200000 requests
Completed 1350000 requests
Finished 1500000 requests
Server Software: LiteSpeed
Server Hostname: 192.168.56.101
Server Port: 80
Document Path: /index.php
Document Length: 19841 bytes
Concurrency Level: 5000
Time taken for tests: 163.910341 seconds
Complete requests: 1500000
Failed requests: 0
Write errors: 0
Keep-Alive requests: 657470
Total transferred: 30208037959 bytes
HTML transferred: 29804908545 bytes
Requests per second: 9151.34 [#/sec] (mean)
Time per request: 546.368 [ms] (mean)
Time per request: 0.109 [ms] (mean, across all concurrent requests)
Transfer rate: 179976.66 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 42 53.5 17 309
Processing: 121 501 114.0 550 864
Waiting: 12 154 62.7 156 534
Total: 134 544 148.4 597 1016
Percentage of the requests served within a certain time (ms)
50% 597
66% 645
75% 666
80% 678
90% 708
95% 730
98% 757
99% 784
100% 1016 (longest request)
CPU Load
Code:
top - 17:42:28 up 1:02, 3 users, load average: 2.86, 1.33, 0.50
Tasks: 103 total, 4 running, 99 sleeping, 0 stopped, 0 zombie
Cpu0 : 29.5%us, 18.2%sy, 0.0%ni, 19.5%id, 4.0%wa, 0.0%hi, 28.8%si, 0.0%st
Cpu1 : 29.6%us, 14.3%sy, 0.0%ni, 35.5%id, 2.0%wa, 0.7%hi, 17.9%si, 0.0%st
Mem: 2059524k total, 2037892k used, 21632k free, 184k buffers
Swap: 2064376k total, 92112k used, 1972264k free, 38816k cached