详解Docker cpu限制分析

本文测试了，Docker容器限制cpu资源使用的几个配置参数。分别使用top和dstat命令分析了资源占有情况。

package main
import (
  "flag"
  "runtime"
  "fmt"
)
func main() {
  cpunum := flag.Int("cpunum", 0, "cpunum")
  flag.Parse()
  fmt.Println("cpunum:", *cpunum)
  runtime.GOMAXPROCS(*cpunum)
  for i := 0; i < *cpunum - 1; i++ {
    go func() {
      for {
      }
    }()
  }
  for {
  }
}

制作了一个测试cpu占用的镜像，镜像默认占满1个核心

FROM busybox
COPY ./full_cpu /full_cpu
RUN chmod +x /full_cpu
ENTRYPOINT ["/full_cpu", "-cpunum"]CMD ["1"]
docker build -t fangfenghua/cpuuseset .
docker push fangfenghua/cpuuseset
docker info
...
Default Runtime: runc
Security Options: seccomp
Kernel Version: 3.10.0-229.el7.x86_64
Operating System: CentOS Linux 7 (Core)
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 993.3 MiB
Name: localhost.localdomain
ID: TU6M:E6WM:PZDN:ULJX:EWKS:
  ...

docker run -it --rm=true fangfenghua/cpuuseset
[root@localhost src]# top
top - 07:23:52 up 1:23, 2 users, load average: 0.61, 1.12, 1.04
Tasks: 154 total,  3 running, 145 sleeping,  6 stopped,  0 zombie
%Cpu(s): 18.0 us, 0.1 sy, 0.0 ni, 81.8 id, 0.0 wa, 0.0 hi, 0.1 si, 0.0 st
KiB Mem : 1017144 total,  422120 free,  171676 used,  423348 buff/cache
KiB Swap: 1040380 total, 1040284 free,    96 used.  688188 avail Mem 
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
20196 root   20  0  3048  720  460 R 101.7 0.1  0:37.56 full_cpu
  1 root   20  0  41536  4028  2380 S  0.0 0.4  0:02.60 systemd
  2 root   20  0    0   0   0 S  0.0 0.0  0:00.04 kthreadd
  3 root   20  0    0   0   0 S  0.0 0.0  0:00.48 ksoftirqd/0
  5 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 kworker/0:0H
  7 root   rt  0    0   0   0 S  0.0 0.0  0:00.69 migration/0  
docker run -it --rm=true fangfenghua/cpuuseset 4
top - 07:27:17 up 1:27, 2 users, load average: 2.41, 1.47, 1.18
Tasks: 159 total,  3 running, 145 sleeping, 11 stopped,  0 zombie
%Cpu(s): 99.6 us, 0.2 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.3 si, 0.0 st
KiB Mem : 1017144 total,  402508 free,  190908 used,  423728 buff/cache
KiB Swap: 1040380 total, 1040284 free,    96 used.  668608 avail Mem 
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
20935 root   20  0  3048  720  452 R 400.0 0.1  0:55.80 full_cpu
  1 root   20  0  41620  4088  2380 S  0.0 0.4  0:02.88 systemd
  2 root   20  0    0   0   0 S  0.0 0.0  0:00.04 kthreadd

在Linux 系统上，可以用来限制docker容器资源占用的参数有：

–cpu-period int              Limit CPU CFS (Completely Fair Scheduler) period