【kubernetes/k8s概念】pod 资源 request 与 limit

Dear 丶 2022-05-22 01:19 258阅读 0赞

# Managing Compute Resources for Containers #

#  #

https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/

#  #

## requests ##

*  requests用于schedule阶段，在调度pod保证所有pod的requests总和小于node能提供的计算能力
 *  requests.cpu被转成docker的--cpu-shares参数，与cgroup cpu.shares功能相同  
    
    
     *  设置容器的cpu的相对权重
     *  该参数在CPU资源不足时生效，根据容器requests.cpu的比例来分配cpu资源
     *  CPU资源充足时，requests.cpu不会限制container占用的最大值，container可以独占CPU
 *  requests.memory没有对应的docker参数，作为k8s调度依据
 *  使用requests来设置各容器需要的最小资源

## limits ##

*  limits限制运行时容器占用的资源
 *  limits.cpu会被转换成docker的–cpu-quota参数。与cgroup cpu.cfs\_quota\_us功能相同  
    
    
     *  限制容器的最大CPU使用率。
     *  cpu.cfs\_quota\_us参数与cpu.cfs\_period\_us结合使用，后者设置时间周期
     *  k8s将docker的–cpu-period参数设置100毫秒。对应着cgroup的cpu.cfs\_period\_us
     *  limits.cpu的单位使用m，千分之一核
 *  limits.memory会被转换成docker的–memory参数。用来限制容器使用的最大内存
 *  当容器申请内存超过limits时会被终止

# 如下代码，转换为docker资源限制 #

#  #

func (m *kubeGenericRuntimeManager) generateLinuxContainerConfig(container *v1.Container, pod *v1.Pod, uid *int64, username string) *runtimeapi.LinuxContainerConfig {
       lc := &runtimeapi.LinuxContainerConfig{
          Resources:       &runtimeapi.LinuxContainerResources{},
          SecurityContext: m.determineEffectiveSecurityContext(pod, container, uid, username),
       }
    
       // set linux container resources
       var cpuShares int64
     cpuRequest := container.Resources.Requests.Cpu() cpuLimit := container.Resources.Limits.Cpu() memoryLimit := container.Resources.Limits.Memory().Value() oomScoreAdj := int64(qos.GetContainerOOMScoreAdjust(pod, container, int64(m.machineInfo.MemoryCapacity)))
       // If request is not specified, but limit is, we want request to default to limit.
       // API server does this for new containers, but we repeat this logic in Kubelet
       // for containers running on existing Kubernetes clusters.
       if cpuRequest.IsZero() && !cpuLimit.IsZero() {
          cpuShares = milliCPUToShares(cpuLimit.MilliValue())
       } else {
          // if cpuRequest.Amount is nil, then milliCPUToShares will return the minimal number
          // of CPU shares.
          cpuShares = milliCPUToShares(cpuRequest.MilliValue())
       }
       lc.Resources.CpuShares = cpuShares
       if memoryLimit != 0 {
          lc.Resources.MemoryLimitInBytes = memoryLimit
       }
       // Set OOM score of the container based on qos policy. Processes in lower-priority pods should
       // be killed first if the system runs out of memory.
       lc.Resources.OomScoreAdj = oomScoreAdj
    
       if m.cpuCFSQuota {
          // if cpuLimit.Amount is nil, then the appropriate default value is returned
          // to allow full usage of cpu resource.
          cpuQuota, cpuPeriod := milliCPUToQuota(cpuLimit.MilliValue())
          lc.Resources.CpuQuota = cpuQuota
          lc.Resources.CpuPeriod = cpuPeriod
       }
    
       return lc
    }