今天发了个链接，可能同时在线的人瞬间比较多，结果网站报503错误，回去打开php-fpm错误日志一看，php-fpm服务挂掉了，报如下错误：
[04-Apr-2016 15:38:04] NOTICE: systemdmonitorintervalsetto 10000ms [05-Apr-2016 19:03:08] WARNING: [poolwww] seemsbusy (youmayneedto increasepm.start_servers, or pm.min/max_spare_servers), spawning 8 children, thereare 0 idle, and 29 totalchildren [05-Apr-2016 19:03:09] WARNING: [poolwww] seemsbusy (youmayneedto increasepm.start_servers, or pm.min/max_spare_servers), spawning 16 children, thereare 0 idle, and 34 totalchildren [05-Apr-2016 19:03:11] WARNING: [poolwww] seemsbusy (youmayneedto increasepm.start_servers, or pm.min/max_spare_servers), spawning 32 children, thereare 0 idle, and 39 totalchildren [05-Apr-2016 19:03:12] WARNING: [poolwww] seemsbusy (youmayneedto increasepm.start_servers, or pm.min/max_spare_servers), spawning 32 children, thereare 0 idle, and 44 totalchildren [05-Apr-2016 19:03:13] WARNING: [poolwww] seemsbusy (youmayneedto increasepm.start_servers, or pm.min/max_spare_servers), spawning 32 children, thereare 0 idle, and 49 totalchildren [05-Apr-2016 19:03:14] WARNING: [poolwww] serverreachedpm.max_children setting (50), considerraisingit
错误提示建议增加pm.start_servers数量，打开我的php-fpm配置：
pm.max_children = 50 ; Thenumberofchild processescreatedonstartup. ; Note: Usedonlywhenpmis setto 'dynamic' ; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2 pm.start_servers = 15 ; Thedesiredminimumnumberofidleserverprocesses. ; Note: Usedonlywhenpmis setto 'dynamic' ; Note: Mandatorywhenpmis setto 'dynamic' pm.min_spare_servers = 5 ; Thedesiredmaximumnumberofidleserverprocesses. ; Note: Usedonlywhenpmis setto 'dynamic' ; Note: Mandatorywhenpmis setto 'dynamic' pm.max_spare_servers = 35
这里pm.start_servers之前我设置为5，注意配置文件也说明start_servers的值默认是max_spare_servers-min_spare_servers的一半。(ps:具体的值要根据服务器配置情况和压力测试得出)
网站服务器是阿里云1G带宽，1G内存，1核CPU配置，关键还在一台机子上装了数据库，redis各种服务。
pm.max_children = 24
static模式下创建的子进程数或dynamic模式下同一时刻允许最大的php-fpm子进程数量
pm.start_servers = 16
动态方式下的起始php-fpm进程数量
pm.min_spare_servers = 12
动态方式下服务器空闲时最小php-fpm进程数量
pm.max_spare_servers = 24
动态方式下服务器空闲时最大php-fpm进程数量
经验人士的总结：
一般php-fpm进程占用20~30m左右的内存就按30m算。如果单独跑php-fpm，动态方式起始值可设置物理内存Mem/30M，由于大家一般Nginx、MySQL都在一台机器上，于是预留一半给它们，即php-fpm进程数为$Mem/2/30。
调整之后的几个值是：
pm = dynamic pm.max_children = 50 pm.start_servers = 15 pm.min_spare_servers = 10 pm.max_spare_servers = 40
重启php-fpm服务：service php70-php-fpm reload，继续使用top命令查看内存使用情况，发现十几个php-fpm启动。
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