FreeBSD和Linux的Nginx静态文件性能对比测试

最近准备换VPS，看到有VPS支持FreeBSD，就打算试试。想了解一下它和linux性能上的差异，就在网上找了些文章看了看。很多文章都提到FreeBSD更适合做前端的文件服务器，它的数据库性能和SMP性能不如linux。不过这些文章要么比较老，要么就是纯粹的口水仗，缺乏翔实的数据支撑。于是还是决定自己多装几台虚拟机测试一下好了。

测试环境：
宿主：
Core i3 530 @ 2.93GHz 双核4线程
16G RAM
Windows 7 64bit

虚拟机软件：
Virtualbox 4.1.2

虚拟机配置：
FreeBSD 7.2 i386 / FreeBSD 8.2 amd64 / Debian 5.0 i386 / CentOS 5.6 i386
双核全速
256M RAM
8GB硬盘
启用硬件虚拟化和IO APIC

各系统用最小安装，然后安装了编译工具链+apache（为了方便使用ab）+php+mysql。www.linuxidc.com之后关掉apache，安装nginx。
FreeBSD使用ports编译安装nginx，Debian分别使用了源自带的和编译的最新稳定版，CentOS使用编译的最新稳定版。FreeBSD的nginx应该默认使用了kqueue，linux默认使用了epoll。
nginx设置为1个worker，开启gzip。

测试使用ApacheBench，测试文件为一个57244 bytes的jquery.js。
除CentOS外，ApacheBench都是2.3版，CentOS是2.0版。

ab -c 10 -n 100000 http://localhost/jquery.js

不多废话了，以下是测试结果：

FreeBSD 7.2 i386 + nginx 0.6.36

Concurrency Level:      10
Time taken for tests:   26.156 seconds
Complete requests:      100000
Failed requests:        0
Write errors:           0
Total transferred:      5747200000 bytes
HTML transferred:       5724400000 bytes
Requests per second:    3823.15 [#/sec] (mean)
Time per request:       2.616 [ms] (mean)
Time per request:       0.262 [ms] (mean, across all concurrent requests)
Transfer rate:          214574.53 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.2      0       4
Processing:     0    2   0.8      2      18
Waiting:        0    1   0.6      1      16
Total:          0    3   0.7      2      18

FreeBSD 8.2 amd64 + nginx 0.8.54

Concurrency Level:      10
Time taken for tests:   24.675 seconds
Complete requests:      100000
Failed requests:        0
Write errors:           0
Total transferred:      5747257344 bytes
HTML transferred:       5724457116 bytes
Requests per second:    4052.62 [#/sec] (mean)
Time per request:       2.468 [ms] (mean)
Time per request:       0.247 [ms] (mean, across all concurrent requests)
Transfer rate:          227455.77 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.2      0       8
Processing:     1    2   0.6      2      19
Waiting:        0    1   0.5      1       9
Total:          1    2   0.6      2      20

Debian 5.0 i386 + nginx 0.6.32

Concurrency Level:      10
Time taken for tests:   9.808 seconds
Complete requests:      100000
Failed requests:        0
Write errors:           0
Total transferred:      5747257472 bytes
HTML transferred:       5724457244 bytes
Requests per second:    10195.98 [#/sec] (mean)
Time per request:       0.981 [ms] (mean)
Time per request:       0.098 [ms] (mean, across all concurrent requests)
Transfer rate:          572254.98 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0      10
Processing:     0    1   1.0      1      94
Waiting:        0    0   0.9      0      94
Total:          0    1   1.0      1      95

Debian 5.0 i386 + nginx 1.0.6

Concurrency Level:      10
Time taken for tests:   9.321 seconds
Complete requests:      100000
Failed requests:        0
Write errors:           0
Total transferred:      5747157471 bytes
HTML transferred:       5724457244 bytes
Requests per second:    10728.92 [#/sec] (mean)
Time per request:       0.932 [ms] (mean)
Time per request:       0.093 [ms] (mean, across all concurrent requests)
Transfer rate:          602156.28 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       7
Processing:     0    1   0.4      1      32
Waiting:        0    0   0.4      0      31
Total:          0    1   0.5      1      32

CentOS 5.6 i386 + nginx 1.0.6

Concurrency Level:      10
Time taken for tests:   9.996502 seconds
Complete requests:      100000
Failed requests:        0
Write errors:           0
Total transferred:      1452132704 bytes
HTML transferred:       1429432704 bytes
Requests per second:    10003.50 [#/sec] (mean)
Time per request:       1.000 [ms] (mean)
Time per request:       0.100 [ms] (mean, across all concurrent requests)
Transfer rate:          141859.42 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       3
Processing:     0    0   0.7      0       9
Waiting:        0    0   0.2      0       6
Total:          0    0   0.7      0       9

整理：

和之前看到的很多文章的观点正相反，在nginx静态文件性能的测试中，FreeBSD表现出了巨大的劣势。

由于这一结果非常奇怪，我又将虚拟机改为单核，并测试了lighttpd，结果依然是linux领先了一倍左右。究竟是什么原因造成如此巨大的差异呢？