I’ve just discovered that WordPress and a couple of other sites I run casually tax my CPU really highly running the PHP scripts (the database is on a separate server). I know WP can cache, so I decided to play around. The result? WP Super-Cache results in a (more than) 10x speed improvement just using the “half cache”. What it’s doing is writing the database queries to disk, so it doesn’t have to figure out the result of the query every time it processes the page.
Here are the actual results.
I’ve just discovered that WordPress and a couple of other sites I run casually tax my CPU really highly running the PHP scripts (the database is on a separate server). I know WP can cache, so I decided to play around. The result? http://ocaoimh.ie/wp-super-cache/ results in a 10x speed improvement just using the “half cache”. What it’s doing is writing the database queries to disk, so it doesn’t have to figure out the result of the query every time it processes the page.
By the way, the CPU is a K6-2 333MHz. I imagine the gain would be smaller on a faster CPU, as a faster CPU processes non-cached results faster => smaller difference between cached / non-cached results => smaller gain.
Here are the actual results.
Results with no cache:
#ab -n 30 "http://www.sirspanky.com/wp/"This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking www.sirspanky.com (be patient).....done
Server Software: Apache/2.2.3
Server Hostname: www.sirspanky.com
Server Port: 80
Document Path: /wp/
Document Length: 56172 bytes
Concurrency Level: 1
Time taken for tests: 170.354564 seconds
Complete requests: 30
Failed requests: 0
Write errors: 0
Total transferred: 1692660 bytes
HTML transferred: 1685160 bytes
Requests per second: 0.18 [#/sec] (mean)
Time per request: 5678.486 [ms] (mean)
Time per request: 5678.486 [ms] (mean, across all concurrent requests)
Transfer rate: 9.70 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 1 1 0.2 1 2
Processing: 5465 5676 349.0 5578 7057
Waiting: 3255 3422 236.1 3378 4581
Total: 5466 5677 349.1 5579 7058
Percentage of the requests served within a certain time (ms)
50% 5579
66% 5602
75% 5610
80% 5635
90% 6010
95% 6747
98% 7058
99% 7058
100% 7058 (longest request)
Results with half cache:
#ab -n 30 "http://www.sirspanky.com/wp/" This is ApacheBench, Version 2.0.40-dev <$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 www.sirspanky.com (be patient).....done Server Software: Apache/2.2.3 Server Hostname: www.sirspanky.com Server Port: 80 Document Path: /wp/ Document Length: 56226 bytes Concurrency Level: 1 Time taken for tests: 8.188850 seconds Complete requests: 30 Failed requests: 29 (Connect: 0, Length: 29, Exceptions: 0) Write errors: 0 Total transferred: 1695860 bytes HTML transferred: 1687940 bytes Requests per second: 3.66 [#/sec] (mean) Time per request: 272.962 [ms] (mean) Time per request: 272.962 [ms] (mean, across all concurrent requests) Transfer rate: 202.23 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 1 1 0.2 1 2 Processing: 55 271 1122.7 61 6215 Waiting: 39 254 1116.1 45 6163 Total: 56 272 1122.9 62 6217 Percentage of the requests served within a certain time (ms) 50% 62 66% 63 75% 64 80% 69 90% 126 95% 133 98% 6217 99% 6217 100% 6217 (longest request)
As you can see, only 1 request (3%) took 6217ms to load with the cache, then the rest load in <200ms. Without the cache, half of the queries take longer than 5579ms and the other half…well they probably take 5578ms 