增加CPU使用率到指定范围

>需求：服务器CPU使用率过低，增加CPU使用率到指定范围

1、安装cpulimit对 CPU 使用率进行控制
```
yum install gcc -y
wget 'http://downloads.sourceforge.net/cpulimit/cpulimit-1.1.tar.gz' --no-check-certificate
tar -zxf cpulimit-1.1.tar.gz
cd cpulimit-1.1
make
cp cpulimit /usr/bin/
```

# 使用
1）限制进程号的程序使用40% cpu利用率
```
cpulimit -p 1313 -l 40
```
2）限制程序google使用40% cpu利用率
```
cpulimit -e google -l 40
```

2、shell脚本增加CPU压力：cputest.sh
```
#! /bin/bash
# filename cputest.sh
endless_loop()
{
echo -ne "i=0;
while true
do
i=i+100;
i=100
done" | /bin/bash &
}

if [ $# != 1 ] ; then
  echo "USAGE: $0 <CPUs>"
  exit 1;
fi
for i in `seq $1`
do
  endless_loop
  pid_array[$i]=$! ;
done

for i in "${pid_array[@]}"; do
  echo 'stopUsage: kill ' $i ';';
done
```
3、执行增加CPU压力的脚本，然后控制观察
```
chmod +x cputest.sh
```
几核CPU就写几
```
sh cputest.sh 1
# stopUsage: kill  21648 ;
```

限制进程号21648使用的CPU利用率为40%
```
cpulimit -p 21648 -l 40 &
```

中断脚本
```
kill 21648
```
PS：增加CPU后限制使用率到指定值40%整合脚本：
```
#! /bin/bash
# filename cputest.sh

# 限制进程号的程序使用40% cpu利用率(可修改)
utilization="40"

endless_loop()
{
echo -ne "i=0;
while true
do
i=i+100;
i=100
done" | /bin/bash &
}

if [ $# != 1 ] ; then
  echo "USAGE: $0 <CPUs>"
  exit 1;
fi
for i in `seq $1`
do
  endless_loop
  pid_array[$i]=$! ;
done

for i in "${pid_array[@]}"; do
    echo 'stopUsage: kill ' $i ';'
    nohup cpulimit -p "$i" -l "$utilization" &
done
```
运行结果如下：
```
[root@web ~]# bash cputest.sh 2
stopUsage: kill  35045 ;
stopUsage: kill  35047 ;
You have new mail in /var/spool/mail/root
[root@web ~]# nohup: appending output to ‘nohup.out’
nohup: appending output to ‘nohup.out’

[root@web ~]# ps -ef | grep limit
root      35048      1  0 00:11 pts/0    00:00:00 cpulimit -p 35045 -l 40
root      35049      1  0 00:11 pts/0    00:00:00 cpulimit -p 35047 -l 40

[root@web ~]# top
top - 00:12:32 up 1 day, 15:18,  5 users,  load average: 1.26, 0.63, 0.30
Tasks: 125 total,   4 running, 121 sleeping,   0 stopped,   0 zombie
%Cpu0  : 40.5 us,  0.0 sy,  0.0 ni, 59.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  : 40.8 us,  0.0 sy,  0.0 ni, 59.2 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :   997956 total,   259040 free,   147584 used,   591332 buff/cache
KiB Swap:  2097148 total,  2096884 free,      264 used.   616408 avail Mem

PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND   
 35045 root      20   0  113280   1200   1020 R  39.2  0.1   0:15.19 bash      
 35047 root      20   0  113280   1200   1020 R  39.2  0.1   0:15.20 bash 
 ```