Author：小怪兽Nikki 微博：@再见了小怪兽
去除http.conf中Include conf/extra/httpd-mpm.conf前的#，以使httpd-mpm.conf中的配置生效。
#Server-pool management (MPM specific)
Include conf/extra/httpd-mpm.conf
一、Apache的默认情况
<pre>
<IfModule mpm_worker_module>
StartServers 3
MinSpareThreads 75
MaxSpareThreads 250
ThreadsPerChild 25
MaxRequestWorkers 400
MaxConnectionsPerChild 0
</IfModule>
</pre>
由此可见，Apache在启动时，按照默认StartServers启动3个子进程，并且由于已经符合最小空闲进程，故不再变化。
h2. 2、startServers*ThreadsPerChild < MinSpareThreads，MinSpareTreads为ThreadsPerChild的整数倍：
<pre>
<IfModule mpm_worker_module>
StartServers 3
MinSpareThreads 100
MaxSpareThreads 250
ThreadsPerChild 25
MaxRequestWorkers 400
MaxConnectionsPerChild 0
</IfModule>
</pre>
[[email protected] extra]# ps -ef|grep httpd
root 43900 1 0 03:37 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 43903 43900 0 03:37 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 43904 43900 0 03:37 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 43911 43900 0 03:37 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 44087 43900 0 03:37 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
root 45907 20322 0 03:37 pts/0 00:00:00 grep httpd
!http://redmine.intra.weibo.com/attachments/download/4957/%E6%97%A0%E6%A0%87%E9%A2%983.png!
由于3个初始的子进程共提供75个线程，故不满足100个最小空闲线程数的要求，所以apache新启动一个子进程来提供额外的线程.
h2. 3、startServers*ThreadsPerChild < MinSpareThreads，MinSpareTreads为ThreadsPerChild的非整数倍：
<pre>
<IfModule mpm_worker_module>
StartServers 3
MinSpareThreads 90
MaxSpareThreads 250
ThreadsPerChild 25
MaxRequestWorkers 400
MaxConnectionsPerChild 0
</IfModule>
</pre>
[[email protected] extra]# ps -ef|grep httpd
root 38933 1 0 03:46 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 38937 38933 0 03:46 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 38938 38933 0 03:46 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 38942 38933 0 03:46 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 39112 38933 0 03:46 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
[[email protected] bin]# sh jingjingtest/test.sh
38937:26
38938:26
38942:26
38937:26
38938:26
38942:26
39112:26
由此可见apache在启动3个子进程后又启动一个子进程，但是并没有给新的子进程新建90-25*3=15个线程，而是也生成26个线程（其中一个为监控线程），新子进程的线程数为：ThreadsPerChild个。
h2. 4、startServers*ThreadsPerChild > MinSpareThreads
<pre>
<IfModule mpm_worker_module>
StartServers 3
MinSpareThreads 10
MaxSpareThreads 250
ThreadsPerChild 25
MaxRequestWorkers 400
MaxConnectionsPerChild 0
</IfModule>
</pre>
[[email protected] extra]# ps -ef|grep httpd
root 21985 1 0 03:53 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 21987 21985 0 03:53 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 21988 21985 0 03:53 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
daemon 21992 21985 0 03:53 ? 00:00:00 /data2/irunner9001/lamp/apache//bin/httpd -k start
root 23846 20322 0 03:53 pts/0 00:00:00 grep httpd
[[email protected] bin]# sh jingjingtest/test.sh
21987:26
21988:26
21992:26
21987:26
21988:26
21992:26
21987:26
21988:26
21992:26
21987:26
21988:26
21992:26
由此可见，当初始启动的线程数已经满足最小空闲线程，而没有超过最大空闲线程，则不会再清除线程。
h2. 5、有请求时，已有线程数-请求数 < 最小空闲线程：
<pre>
<IfModule mpm_worker_module>
StartServers 3
MinSpareThreads 75
MaxSpareThreads 250
ThreadsPerChild 25
MaxRequestWorkers 400
MaxConnectionsPerChild 0
</IfModule>
</pre>
发送请求：
> ab -n 10000 -c 10 http://10.210.228.50:9001/
各子进程线程情况：
---
19202:26
19203:26
19210:26
---
19202:26
19203:26
19210:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
---
19202:26
19203:26
19210:26
20082:26
由此可以看出，初始有3个子进程，共有3*25=75个线程，当有10个请求到来，存在空闲线程不足minSpareThread个，则新启动一个子进程。