一般情况下，我们认为 一个进程在启动的时候，从当前环境里继承了
ulimit 的各个限制，一旦启动就无法修改了。

一般情况下是需要修改系统的ulimit 配置 ，重新登录，然后重新启动引用。

前面我们也说了在centos6.2 之后，/etc/security/limits.d/90-nproc.conf  这文件里定义了各个进程默认的限制。

如果一个进程，已经启动了，而发现他的limit限制没有改，又不能随便重启怎么办呢？


centos 6.2之后的系统是可以的。


vi /proc/$pid/limits

[code]
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            10485760             unlimited            bytes
Max core file size        0                    unlimited            bytes
Max resident set          unlimited            unlimited            bytes
Max processes             10240                10240                processes
Max open files            65536                65536                files
Max locked memory         65536                65536                bytes
Max address space         unlimited            unlimited            bytes
Max file locks            unlimited            unlimited            locks
Max pending signals       515066               515066               signals
Max msgqueue size         819200               819200               bytes
Max nice priority         0                    0
Max realtime priority     0                    0
Max realtime timeout      unlimited            unlimited            us
[/code]
[postgres@bbs-userdb-239-230 31141]$ 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) 515066
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65536
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 10240
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited


我们修改下看看 。

[code]
[postgres@bbs-userdb-239-230 31141]$ echo -n 'Max processes=1024:1024' > limits 
[postgres@bbs-userdb-239-230 31141]$ grep process  limits
Max processes             1024                 1024                 processes
[postgres@bbs-userdb-239-230 31141]$ 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) 515066
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65536
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1024
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
[/code]
 
看到了么，修改了哦


当然了对于以前版本的，必须要重启应用才能解决的，也有一个比较BT 的方案

用gdb  勾住进程然后修改进程的core dump 空间里的值。

之前用gdb 来修改过mysql 的只读参数，是可行的， 修改这个也是可行的。

转一个网上找到的脚本放这里：

[code]

#!/bin/bash

f="0"
while getopts ":c:d:e:f:i:l:m:n:p:q:r:s:t:u:v:x" opt; do
  if [ "$f" == "1" ]; then
    echo "too many arguments" >&2;
    exit 1
  fi
  f="1"
  v="$OPTARG"
  case $opt in
  c) r=4  ;; # RLIMIT_CORE       core file size
  d) r=2  ;; # RLIMIT_DATA       data seg size  
  e) r=13 ;; # RLIMIT_NICE       scheduling priority 
  f) r=1  ;; # RLIMIT_FSIZE      file size
  i) r=11 ;; # RLIMIT_SIGPENDING pending signals
  l) r=8  ;; # RLIMIT_MEMLOCK    max locked memory
  m) r=5  ;; # RLIMIT_RSS        max memory size
  n) r=7  ;; # RLIMIT_NOFILE     open files
  q) r=12 ;; # RLIMIT_MSGQUEUE   POSIX message queues
  r) r=14 ;; # RLIMIT_RTPRIO     real-time priority
  s) r=3  ;; # RLIMIT_STACK      stack size
  t) r=0  ;; # RLIMIT_CPU        cpu time
  u) r=6  ;; # RLIMIT_NPROC      max user processes
  v) r=9  ;; # RLIMIT_AS         virtual memory
  x) r=10 ;; # RLIMIT_LOCKS      file locks

  ?) echo "bad argument $opt" >&2; exit 1 ;;
  esac
done

shift $(($OPTIND - 1))

if echo "$v" | grep -q -E "^\-?[0-9]+$"; then
  true
else
  echo "bad rlimti value $v" >&2
  exit 2
fi

if [ `echo "$v==-1 || ($v>=0 && $v<1048576)"|bc` == '0' ];then
  echo "bad rlimti value $v" >&2
  exit 2
fi

pid=$1
bin=`readlink /proc/$pid/exe`
if [ -z "$bin" ]; then
  echo "process $pid not found" >&2
  exit 3
fi

cmd='
set $rlim=&{-1ll,-1ll}
print getrlimit('$r',$rlim)
set *$rlim[0]='$v'
print setrlimit('$r',$rlim)
quit
'

result=`echo "$cmd" | gdb $bin $pid 2>/dev/null | grep '(gdb) \$2 ='`
result="${result##*= }"
exit $result

[/code]