业务量太大的时候，lnmp下的php-fpm就卡死了。查了半天，发现有个pcscd.comm占用了好几千个连接数，极其壮观：

查linux官方文档，解释这个服务：
pcscd is the daemon program for pcsc-lite and the MuscleCard framework. It is a resource manager that coordinates communications with smart card readers and smart cards and cryptographic tokens that are connected to the system.pcscd is normally started at boot time from /etc/init.d/pcscd. It allows applications to access smart cards and readers without knowing details of the card or reader.
原来是智能卡的支持服务，果断关掉：
[admin@APP5 ~]$ sudo service pcscd stop
Stopping PC/SC smart card daemon (pcscd): [ OK ]
查看连接数，瞬间降下来了。
然后chkconfig 把pcscd服务自启动给禁用掉：
chkconfig pcscd off
搞定。
至于为什么启动了这么多连接数，具体原因未明，估计是linux虚拟机系统没配置好。