设置ulimit

centos服务器设置ulimit，ulimit是指服务器允许的最大打开文件数目

查看ulimit

ulimit -a

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 127567
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 655350
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4096
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

open files默认是1024，有时候会不够，可以进行修改

临时修改

# -H 表示硬限制
# -S 表示软限制
# 如果不加-H和-S则两个一起修改
ulimit -n 655360

永久修改

配置文件在/etc/security/limits.conf

可以进行修改

1	* - nofile 655360

查看某进程的limits

在/proc/${pid}/limits文件中存储着对应pid的limit信息

cat /proc/31925/limits 
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            8388608              unlimited            bytes     
Max core file size        0                    unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             61371                61371                processes 
Max open files            1024                 4096                 files     
Max locked memory         65536                65536                bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       61371                61371                signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us