早先问过BleakWind，他认为，给别人做的话MySQL内存表做会话比较好一些，因为MySQL内存表做Session更容易维护（可以制作安装脚本）。这个周末，我进行了一些测试，测试MySQL MyISAM表做会话（对时间给不给索引）、内存表做会话、MemCache做会话的效率比较。
定义会话Session类：
定义会话处理器接口（Session_Handler_Interface)：
实现MySQL内存表Session处理器：
实现MemCache会话处理器：
MySQL内存表测试程序：
MemCache会话测试代码：
MySQL会话表如下：
CREATE TABLE `session` (
`id` char(32) COLLATE utf8_unicode_ci NOT NULL,
`name` varchar(20) COLLATE utf8_unicode_ci NOT NULL,
`ip` varchar(15) COLLATE utf8_unicode_ci NOT NULL,
`time` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MEMORY DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
测试结果：
MemCache：
======================================================================================
Concurrency Level: 30
Time taken for tests: 18.234375 seconds
Complete requests: 10000
Failed requests: 0
Write errors: 0
Total transferred: 2774781 bytes
HTML transferred: 280000 bytes
Requests per second: 548.41 [#/sec] (mean)
Time per request: 54.703 [ms] (mean)
Time per request: 1.823 [ms] (mean, across all concurrent requests)
Transfer rate: 148.57 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 1.9 0 31
Processing: 0 53 12.1 46 328
Waiting: 0 52 11.9 46 328
Total: 0 53 12.1 46 328
Percentage of the requests served within a certain time (ms)
50% 46
66% 62
75% 62
80% 62
90% 62
95% 62
98% 62
99% 78
100% 328 (longest request)
MySQL内存表：
=================================================================================
Concurrency Level: 30
Time taken for tests: 20.375000 seconds
Complete requests: 10000
Failed requests: 4694
(Connect: 0, Length: 4694, Exceptions: 0)
Write errors: 0
Total transferred: 3118440 bytes
HTML transferred: 623048 bytes
Requests per second: 490.80 [#/sec] (mean)
Time per request: 61.125 [ms] (mean)
Time per request: 2.038 [ms] (mean, across all concurrent requests)
Transfer rate: 149.45 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 0 1.9 0 31
Processing: 0 60 7.6 62 125
Waiting: 0 59 7.6 62 125
Total: 0 60 7.5 62 125
Percentage of the requests served within a certain time (ms)
50% 62
66% 62
75% 62
80% 62
90% 62
95% 62
98% 78
99% 78
100% 125 (longest request)
其他测试：
将MySQL实现的数据库引擎改为 MyISAM（依然为 并发 30 测试 10000 次） 结果为：
Requests per second: 440.17 [#/sec] (mean)
Percentage of the requests served within a certain time (ms)
50% 62
66% 62
75% 78
80% 78
90% 78
95% 78
98% 78
99% 78
100% 640 (longest request)
为MyISAM表的 time 列增加索引（因为 会话表 读写次数几乎相等，因此应该效果不明显），结果为：
Requests per second: 441.08 [#/sec] (mean)
Percentage of the requests served within a certain time (ms)
50% 62
66% 62
75% 78
80% 78
90% 78
95% 78
98% 109
99% 109
100% 156 (longest request)
=================================================================================
结论：
MemCache做会话效率最高，也最灵活，但目前尝不支持查看谁在线等功能，附加的，只能自己增加一个数组记录在线用户、以及最后活跃时间并实现gc等。
MySQL内存表做会话效率也相当的高，另外一个有点是，MySQL内存表似乎更稳定，longest request （125ms）明显的短于 MemCache的（328ms）。不过缺点是，存储的字段数以及字段长度受限。
MySQL MyISAM表做会话在这里居然也达到了440的rps，真不简单。不过您要是等半个小时在测试一次，您就会明白MyISAM表的缺点了，页面几乎崩溃。MyISAM表的缺点是，一旦其中有较多的碎片，这个数据库几乎都不可用了，您注释掉 gc 的代码在这里貌似可以获得更好的效率表现(^_^、当然也可以定时的Optimizer，概率触发或者Cron定时启动也不错）
MyISAM表对time列增加索引对每秒完成的请求数没什么影响，不过有一点需要注意的是，增加索引后，每次完成 request的时间更均匀了,longest request从640ms跌到了156ms。为time列增加索引有助于让完成请求的时间变均匀。
测试平台：
Acer Aspire 4520G：
CPU：AMD Athlon 64 * 2 TK-55
RAM: IG
OS: Windows XP sp2
Web Server: Apache 2.26
PHP: PHP5.25