PHP在性能上相对于其他编译型语言来说算不上突出，但是使用了Opcode缓存后性能提升还是很明显的。常见的缓存加速组件主要有 eAccelerator,XCache,APC本文主要介绍APC的安装使用。
APC，全称是Alternative PHP Cache，官方翻译叫"可选PHP缓存"。它为我们提供了缓存和优化PHP的中间代码的框架。 APC的缓存分两部分:系统缓存和用户数据缓存。
系统缓存
它是指APC把PHP文件源码的编译结果缓存起来，然后在每次调用时先对比时间标记。如果未过期，则使用缓存的中间代码运行。默认缓存3600s(一小时)。但是这样仍会浪费大量CPU时间。因此可以在php.ini中设置system缓存为永不过期(apc.ttl=0)。不过如果这样设置，改运php代码后需要重启WEB服务器。目前使用较多的是指此类缓存。
用户数据缓存
缓存由用户在编写PHP代码时用apc_store和apc_fetch函数操作读取、写入的。如果数据量不大的话，可以一试。如果数据量大，使用类似memcache此类的更加专著的内存缓存方案会更好。
APC模块的安装
最简单的方法是直接使用pecl，在命令行下输入：/usr/local/php/bin/pecl install apc
然后按照提示一步步完成即可，示例如下：
[root@iZ23bm1tc0pZ ~]# /usr/local/php/bin/pecl install apc
downloading APC-3.1.13.tgz ...
Starting to download APC-3.1.13.tgz (171,591 bytes)
.....................................done: 171,591 bytes
55 source files, building
running: phpize
Configuring for:
PHP Api Version: 20100412
Zend Module Api No: 20100525
Zend Extension Api No: 220100525
Enable internal debugging in APC [no] : no
Enable per request file info about files used from the APC cache [no] : no
Enable spin locks (EXPERIMENTAL) [no] : no
Enable memory protection (EXPERIMENTAL) [no] : no
Enable pthread mutexes (default) [no] : no
Enable pthread read/write locks (EXPERIMENTAL) [yes] : yes
然后重启服务器即可：
lnmp nginx restart
先看一下没有使用apc情况下的压测结果：
[root@iZ23bm1tc0pZ ~]# ab -n1000 -c100 http://zfsphp.cn/index.php
This is ApacheBench, Version 2.3 <$Revision: 1706008 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking zfsphp.cn (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests
Server Software: nginx
Server Hostname: zfsphp.cn
Server Port: 80
Document Path: /index.php
Document Length: 14341 bytes
Concurrency Level: 100
Time taken for tests: 15.517 seconds
Complete requests: 1000
Failed requests: 0
Total transferred: 14544000 bytes
HTML transferred: 14341000 bytes
Requests per second: 64.45 [#/sec] (mean)
Time per request: 1551.671 [ms] (mean)
Time per request: 15.517 [ms] (mean, across all concurrent requests)
Transfer rate: 915.34 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 2 4.8 0 17
Processing: 46 1481 277.0 1560 1638
Waiting: 42 1481 277.1 1560 1638
Total: 58 1482 272.8 1560 1638
Percentage of the requests served within a certain time (ms)
50% 1560
66% 1576
75% 1582
80% 1587
90% 1602
95% 1612
98% 1622
99% 1629
100% 1638 (longest request)
可见最大吞吐率只有64.45reqs/s
然后我们开启apc，测试结果如下：
[root@iZ23bm1tc0pZ ~]# ab -n1000 -c100 http://zfsphp.cn/index.php
This is ApacheBench, Version 2.3 <$Revision: 1706008 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking zfsphp.cn (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests
Server Software: nginx
Server Hostname: zfsphp.cn
Server Port: 80
Document Path: /index.php
Document Length: 14341 bytes
Concurrency Level: 100
Time taken for tests: 7.122 seconds
Complete requests: 1000
Failed requests: 0
Total transferred: 14544000 bytes
HTML transferred: 14341000 bytes
Requests per second: 140.41 [#/sec] (mean)
Time per request: 712.189 [ms] (mean)
Time per request: 7.122 [ms] (mean, across all concurrent requests)
Transfer rate: 1994.29 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 1 2.4 0 10
Processing: 23 677 125.3 705 775
Waiting: 22 677 125.4 705 775
Total: 30 678 123.1 705 775
Percentage of the requests served within a certain time (ms)
50% 705
66% 719
75% 726
80% 730
90% 742
95% 750
98% 760
99% 765
100% 775 (longest request)
可见吞吐率提高了一倍多，达到140.41reqs/s。
然后，我们在开启动态内容缓存(楼主的博客用的是Smarty缓存)，测试结果如下：
[root@iZ23bm1tc0pZ ~]# ab -n1000 -c100 http://zfsphp.cn/index.php
This is ApacheBench, Version 2.3 <$Revision: 1706008 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking zfsphp.cn (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests
Server Software: nginx
Server Hostname: zfsphp.cn
Server Port: 80
Document Path: /index.php
Document Length: 14341 bytes
Concurrency Level: 100
Time taken for tests: 2.263 seconds
Complete requests: 1000
Failed requests: 0
Total transferred: 14544000 bytes
HTML transferred: 14341000 bytes
Requests per second: 441.98 [#/sec] (mean)
Time per request: 226.255 [ms] (mean)
Time per request: 2.263 [ms] (mean, across all concurrent requests)
Transfer rate: 6277.49 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 1 3.1 0 12
Processing: 18 215 38.1 222 255
Waiting: 18 215 38.3 222 255
Total: 26 216 35.6 223 255
Percentage of the requests served within a certain time (ms)
50% 223
66% 230
75% 232
80% 234
90% 237
95% 239
98% 240
99% 243
100% 255 (longest request)
这一次吞吐率居然达到441.98reqs/s，提高了三倍多，相比最初的64.45reqs/s提高了近7倍，可见使用apc的opcode缓存配合Smarty缓存，对网站性能的优化效果还是相当明显的。