整理一下Nginx使用的php-fpm的两种进程管理方式及优化!
例:php5.3.8 php-fpm.conf 进程管理配置信息:
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# vim /usr/local/php/etc/php-fpm.conf
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; Choose how the process manager will control the number of child processes.
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; Possible Values:
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; static - a fixed number (pm.max_children) of child processes;
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; dynamic - the number of child processes are set dynamically based on the
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; following directives:
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; pm.max_children - the maximum number of children that can
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; be alive at the same time.
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; pm.start_servers - the number of children created on startup.
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; pm.min_spare_servers - the minimum number of children in 'idle'
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; state (waiting to process). If the number
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; of 'idle' processes is less than this
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; number then some children will be created.
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; pm.max_spare_servers - the maximum number of children in 'idle'
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; state (waiting to process). If the number
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; of 'idle' processes is greater than this
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; number then some children will be killed.
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; Note: This value is mandatory.
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pm = dynamic
由上面一段文字可知，对于进程的管理存在两种风格——static和dynamic
如果设置成static，进程数自始至终都是pm.max_children指定的数量，pm.start_servers，pm.min_spare_servers，pm.max_spare_servers配置将没有作用。
如果设置成dynamic，则进程数是动态的，最开始是pm.start_servers指定的数量，如果请求较多，则会自动增加，但不超过pm.max_children指定的数量，同时保证空闲的进程数不小于pm.min_spare_servers，如果进程数较多，也会进行相应清理，保证多余的进程数不多于pm.max_spare_servers
这两种不同的进程管理方式，可以根据服务器的实际需求来进行调整。
参数解释:
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; The number of child processes to be created when pm is set to 'static' and the
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; maximum number of child processes to be created when pm is set to 'dynamic'.
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; This value sets the limit on the number of simultaneous requests that will be
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; served. Equivalent to the ApacheMaxClients directive with mpm_prefork.
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; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP
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; CGI.
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; Note: Used when pm is set to either 'static' or 'dynamic'
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; Note: This value is mandatory.
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pm.max_children = 50
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; The number of child processes created on startup.
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; Note: Used only when pm is set to 'dynamic'
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; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2
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pm.start_servers = 20
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; The desired minimum number of idle server processes.
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; Note: Used only when pm is set to 'dynamic'
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; Note: Mandatory when pm is set to 'dynamic'
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pm.min_spare_servers = 5
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; The desired maximum number of idle server processes.
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; Note: Used only when pm is set to 'dynamic'
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; Note: Mandatory when pm is set to 'dynamic'
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pm.max_spare_servers = 35
风格:static 此时查看进程数固定为13个
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#假设设置的参数
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pm = static
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pm.max_children=13
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[root@localhost]# ps -axu | grep php-fpm
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root 4423 0.0 0.4 295680 4288 ? Ss 13:27 0:00 php-fpm: master process (/usr/local/php/etc/php-fpm.conf)
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www 4424 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4425 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4426 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4427 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4428 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4429 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4430 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4431 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4432 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4433 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4434 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4435 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4436 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
dynamic风格下必须遵守两个法则
1.pm.min_spare_servers<=pm.start_servers<=pm.max_spare_servers
2.pm.max_children>=pm.max_spare_servers
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#风格:dynamic
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pm = dynamic
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pm.max_children=20
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pm.start_servers=5
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pm.min_spare_servers=5
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pm.max_spare_servers=20
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[root@localhost]# ps -axu | grep php-fpm
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root 4423 0.0 0.4 295680 4288 ? Ss 13:27 0:00 php-fpm: master process (/usr/local/php/etc/php-fpm.conf)
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www 4424 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4425 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4426 0.0 0.4 295680 3984 ? S 13:27 0:00 php-fpm: pool www
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www 4427 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
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www 4428 0.0 0.4 295680 3988 ? S 13:27 0:00 php-fpm: pool www
进程参数设定值方式及优化
那么，对于我们的服务器，选择哪种执行方式比较好呢？事实上，跟Apache一样，运行的PHP程序在执行完成后，或多或少会有内存泄露的问题。这也是为什么开始的时候一个php-fpm进程只占用3M左右内存，运行一段时间后就会上升到20-30M的原因了。
对于内存大的服务器（比如8G以上）来说，指定静态的max_children实际上更为妥当，因为这样不需要进行额外的进程数目控制，会提高效率。因为频繁开关php-fpm进程也会有时滞，所以内存够大的情况下开静态效果会更好。数量也可以根据 内存/30M 得到，比如8GB内存可以设置为200，那么php-fpm耗费的内存就能控制在 4G-6G的样子。如果内存稍微小点，比如1G，那么指定静态的进程数量更加有利于服务器的稳定。这样可以保证php-fpm只获取够用的内存，将不多的内存分配给其他应用去使用，会使系统的运行更加畅通。
对于小内存的服务器来说，比如256M内存的VPS，即使按照一个20M的内存量来算，10个php-cgi进程就将耗掉200M内存，那系统的崩溃就应该很正常了。因此应该尽量地控制php-fpm进程的数量，大体明确其他应用占用的内存后，给它指定一个静态的小数量，会让系统更加平稳一些。或者使用动态方式，因为动态方式会结束掉多余的进程，可以回收释放一些内存，所以推荐在内存较少的服务器或VPS上使用。具体最大数量根据 内存/20M 得到。比如说512M的VPS，建议pm.max_spare_servers设置为20。至于pm.min_spare_servers，则建议根据服务器的负载情况来设置，比较合适的值在5~10之间。
