Randomness from RES

Benchmarking of MySQL Persistent Connections vs Non-Persistent Connections

This post will be about the what always seems to be a hot topic among PHPers about what connection type to use when connection to a MySQL database.

I used MySQL 5.0.45, PHP 5.2.4 for this benchmarking. You can download the same sample MySQL database that is used for this set of benchmarking by visiting http://dev.mysql.com/doc/#sampledb. In the list of example databases, choose the one named ‘sakila’.

For each connection type I will run three tests to see compensate for variations in tests. I will be using http_load to do the benchmarking of the connection file. To view each of the connection files, download the file bundle at the end of this post.

Below is the benchmark command with the options used for each run.

./http_load -verbose -parallel 20 -seconds 600 urls.txt

The urls.txt file contains the following:

http://127.0.0.1/mysql_connection_bench_{CONNECT_TYPE}.php

Between each benchmark run I will restart both Apache and MySQL.

Results for the standard MySQL functions in PHP using mysql_connect.

Run #1:

11024 fetches, 20 max parallel, 44096 bytes, in 600.007 seconds
4 mean bytes/connection
18.3731 fetches/sec, 73.4925 bytes/sec
msecs/connect: 0.22087 mean, 48.992 max, 0.03 min
msecs/first-response: 1087.74 mean, 2880.95 max, 355.012 min
HTTP response codes: code 200 — 11024

Run #2:

10895 fetches, 20 max parallel, 43580 bytes, in 600.004 seconds
4 mean bytes/connection
18.1582 fetches/sec, 72.6328 bytes/sec
msecs/connect: 0.219867 mean, 48.58 max, 0.031 min
msecs/first-response: 1100.1 mean, 2623.47 max, 369.341 min
HTTP response codes: code 200 — 10895

Run #3:

11134 fetches, 20 max parallel, 44536 bytes, in 600.003 seconds
4 mean bytes/connection
18.5566 fetches/sec, 74.2264 bytes/sec
msecs/connect: 0.217796 mean, 42.036 max, 0.03 min
msecs/first-response: 1076.59 mean, 3079.73 max, 270.734 min
HTTP response codes: code 200 — 11134

Results for the standard MySQL functions in PHP using mysql_pconnect.

Run #1:

10982 fetches, 20 max parallel, 43928 bytes, in 600.025 seconds
4 mean bytes/connection
18.3026 fetches/sec, 73.2103 bytes/sec
msecs/connect: 0.216663 mean, 69.795 max, 0 min
msecs/first-response: 1091.52 mean, 3166.82 max, 254.36 min
HTTP response codes: code 200 — 10982

Run #2:

11002 fetches, 20 max parallel, 44008 bytes, in 600.001 seconds
4 mean bytes/connection
18.3366 fetches/sec, 73.3465 bytes/sec
msecs/connect: 0.20555 mean, 47.176 max, 0.031 min
msecs/first-response: 1089.51 mean, 2953.82 max, 414.826 min
HTTP response codes: code 200 — 11002

Run #3:

11196 fetches, 20 max parallel, 44784 bytes, in 600 seconds
4 mean bytes/connection
18.66 fetches/sec, 74.6399 bytes/sec
msecs/connect: 0.2013 mean, 22.478 max, 0.03 min
msecs/first-response: 1070.5 mean, 2506.02 max, 448.161 min
HTTP response codes: code 200 — 11196

Results for non-persistent connections with PDO_MYSQL.

Run #1:

10995 fetches, 20 max parallel, 43980 bytes, in 600.008 seconds
4 mean bytes/connection
18.3248 fetches/sec, 73.299 bytes/sec
msecs/connect: 0.203731 mean, 17.309 max, 0.029 min
msecs/first-response: 1090.44 mean, 2852.34 max, 358.45 min
HTTP response codes: code 200 — 10995

Run #2:

10971 fetches, 20 max parallel, 43884 bytes, in 600.002 seconds
4 mean bytes/connection
18.285 fetches/sec, 73.1398 bytes/sec
msecs/connect: 0.21357 mean, 32.036 max, 0 min
msecs/first-response: 1092.36 mean, 3515.71 max, 456.688 min
HTTP response codes: code 200 — 10971

Run #3:

11161 fetches, 20 max parallel, 44644 bytes, in 600.001 seconds
4 mean bytes/connection
18.6016 fetches/sec, 74.4065 bytes/sec
msecs/connect: 0.20571 mean, 31.679 max, 0.031 min
msecs/first-response: 1073.96 mean, 2539.06 max, 351.236 min
HTTP response codes: code 200 — 11161

Results for persistent connections with PDO_MYSQL.

Run #1:

10347 fetches, 20 max parallel, 41388 bytes, in 600.006 seconds
4 mean bytes/connection
17.2448 fetches/sec, 68.9793 bytes/sec
msecs/connect: 0.253049 mean, 96.354 max, 0 min
msecs/first-response: 1158.52 mean, 2596.78 max, 282.647 min
HTTP response codes: code 200 — 10347

Run #2:

11106 fetches, 20 max parallel, 44424 bytes, in 600.008 seconds
4 mean bytes/connection
18.5098 fetches/sec, 74.0391 bytes/sec
msecs/connect: 0.226898 mean, 51.29 max, 0.03 min
msecs/first-response: 1079.29 mean, 2393.4 max, 311.85 min
HTTP response codes: code 200 — 11106

Run #3:

10978 fetches, 20 max parallel, 43912 bytes, in 600.029 seconds
4 mean bytes/connection
18.2958 fetches/sec, 73.1831 bytes/sec
msecs/connect: 0.210895 mean, 30.339 max, 0 min
msecs/first-response: 1091.98 mean, 3455.6 max, 373.751 min
HTTP response codes: code 200 — 10978

Results Analysis

• mysql_connect
  • Average requests per second: 18.3626
  • Average requests completed: 11,017
• mysql_pconnect
  • Average requests per second: 18.4330
  • Average requests completed: 11,060
• PDO_MySQL non-persistent
  • Average requests per second: 18.4038
  • Average requests completed: 11,042
• PDO_MySQL persistent
  • Average requests per second: 18.0168
  • Average requests completed: 10,810

Basically what the numbers above shows us is that in an isolated environment it makes no difference which connection type you are going to use. My past experience in live heavily trafficked environment says that using non-persistent connections is better than using persistent connections. Where this difference comes shows itself the most is when an apache thread will hang and still hold the persistent connection to mysql preventing other apache processes from connecting. By tweaking your apache and mysql settings you can achieve very good performance with non-persistent connections.

Source files for this benchmarking test.