linux cpu占用率如何看
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2022-10-28
kubernetes入门到实战（七）资源管理和服务质量
kubernetes入门到实战（七）资源管理和服务质量
1. Pod资源管理
1.1 resource定义
容器运行过程中需要分配所需的资源，如何与cggroup联动配合呢？答案是通过定义resource来实现资源的分配，资源的分配单位主要是cpu和memory，资源的定义分两种：requests和limits，requests表示请求资源，主要用于初始kubernetes调度pod时的依据，表示必须满足的分配资源;limits表示资源的限制，即pod不能超过limits定义的限制大小，超过则通过cggroup限制，pod中定义资源可以通过下面四个字段定义：
spec.container[].resources.requests.cpu 请求cpu资源的大小，如0.1个cpu和100m表示分配1/10个cpu； spec.container[].resources.requests.memory 请求内存大小，单位可用M，Mi，G，Gi表示； spec.container[].resources.limits.cpu 限制cpu的大小，不能超过阀值，cggroup中限制的值； spec.container[].resources.limits.memory 限制内存的大小，不能超过阀值，超过会发生OOM；
1、开始学习如何定义pod的resource资源,如下以定义nginx-demo为例，容器请求cpu资源为250m，限制为500m，请求内存资源为128Mi，限制内存资源为256Mi，当然也可以定义多个容器的资源，多个容器相加就是pod的资源总资源，如下：
[root@node-1 demo]#cat nginx-resource.yaml apiVersion: v1 kind: Pod metadata: name: nginx-demo labels: name: nginx-demo spec: containers: - name: nginx-demo image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 0.25 memory: 128Mi limits: cpu: 500m memory: 256Mi
2、应用pod的配置定义(如之前的pod还存在，先将其删除kubectl delete pod
[root@node-1 demo]# kubectl apply -f nginx-resource.yaml pod/nginx-demo created
3、查看pod资源的分配详情
[root@node-1 demo]# kubectl get pods
NAME READY STATUS RESTARTS AGE
demo-7b86696648-8bq7h 1/1 Running 0 12d
demo-7b86696648-8qp46 1/1 Running 0 12d
demo-7b86696648-d6hfw 1/1 Running 0 12d
nginx-demo 1/1 Running 0 94s
[root@node-1 demo]# kubectl describe pods nginx-demo
Name: nginx-demo
Namespace: default
Priority: 0
Node: node-3/10.254.100.103
Start Time: Sat, 28 Sep 2019 12:10:49 +0800
Labels: name=nginx-demo
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-demo"},"name":"nginx-demo","namespace":"default"},"sp...
Status: Running
IP: 10.244.2.13
Containers:
nginx-demo:
Container ID: docker://55d28fdc992331c5c58a51154cd072cd6ae37e03e05ae829a97129f85eb5ed79
Image: nginx:1.7.9
Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Sat, 28 Sep 2019 12:10:51 +0800
Ready: True
Restart Count: 0
Limits: #限制资源
cpu: 500m
memory: 256Mi
Requests: #请求资源
cpu: 250m
memory: 128Mi
Environment:
4、Pod的资源如何分配呢？毫无疑问是从node上分配的，当我们创建一个pod的时候如果设置了requests，kubernetes的调度器kube-scheduler会执行两个调度过程：filter过滤和weight称重，kube-scheduler会根据请求的资源过滤，把符合条件的node筛选出来，然后再进行排序，把最满足运行pod的node筛选出来，然后再特定的node上运行pod。调度算法和细节可以参考下kubernetes调度算法介绍。如下是node-3节点资源的分配详情：
[root@node-1 ~]# kubectl describe node node-3
...省略...
Capacity: #节点上资源的总资源情况，1个cpu，2g内存，110个pod
cpu: 1
ephemeral-storage: 51473888Ki
hugepages-2Mi: 0
memory: 1882352Ki
pods: 110
Allocatable: #节点容许分配的资源情况，部分预留的资源会排出在Allocatable范畴
cpu: 1
ephemeral-storage: 47438335103
hugepages-2Mi: 0
memory: 1779952Ki
pods: 110
System Info:
Machine ID: 0ea734564f9a4e2881b866b82d679dfc
System UUID: FFCD2939-1BF2-4200-B4FD-8822EBFFF904
Boot ID: 293f49fd-8a7c-49e2-8945-7a4addbd88ca
Kernel Version: 3.10.0-957.21.3.el7.x86_64
OS Image: CentOS Linux 7 (Core)
Operating System: linux
Architecture: amd64
Container Runtime Version: docker://18.6.3
Kubelet Version: v1.15.3
Kube-Proxy Version: v1.15.3
PodCIDR: 10.244.2.0/24
Non-terminated Pods: (3 in total) #节点上运行pod的资源的情况，除了nginx-demo之外还有多个pod
Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits AGE
--------- ---- ------------ ---------- --------------- ------------- ---
default nginx-demo 250m (25%) 500m (50%) 128Mi (7%) 256Mi (14%) 63m
kube-system kube-flannel-ds-amd64-jp594 100m (10%) 100m (10%) 50Mi (2%) 50Mi (2%) 14d
kube-system kube-proxy-mh2gq 0 (0%) 0 (0%) 0 (0%) 0 (0%) 12d
Allocated resources: #已经分配的cpu和memory的资源情况
(Total limits may be over 100 percent, i.e., overcommitted.)
Resource Requests Limits
-------- -------- ------
cpu 350m (35%) 600m (60%)
memory 178Mi (10%) 306Mi (17%)
ephemeral-storage 0 (0%) 0 (0%)
Events:
1.2 资源分配原理
Pod的定义的资源requests和limits作用于kubernetes的调度器kube-sheduler上，实际上cpu和内存定义的资源会应用在container上，通过容器上的cggroup实现资源的隔离作用，接下来我们介绍下资源分配的原理。
spec.containers[].resources.requests.cpu 作用在CpuShares，表示分配cpu 的权重，争抢时的分配比例 spec.containers[].resources.requests.memory 主要用于kube-scheduler调度器，对容器没有设置意义 spec.containers[].resources.limits.cpu 作用CpuQuota和CpuPeriod，单位为微秒，计算方法为：CpuQuota/CpuPeriod，表示最大cpu最大可使用的百分比，如500m表示允许使用1个cpu中的50%资源 spec.containers[].resources.limits.memory 作用在Memory，表示容器最大可用内存大小，超过则会OOM
以上面定义的nginx-demo为例，研究下pod中定义的requests和limits应用在docker生效的参数：
1、查看pod所在的node节点，nginx-demo调度到node-3节点上
[root@node-1 ~]# kubectl get pods -o wide nginx-demo
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-demo 1/1 Running 0 96m 10.244.2.13 node-3
2、获取容器的id号，可以通过kubectl describe pods nginx-demo的containerID获取到容器的id，或者登陆到node-3节点通过名称过滤获取到容器的id号，默认会有两个pod：一个通过pause镜像创建，另外一个通过应用镜像创建
[root@node-3 ~]# docker container list |grep nginx 55d28fdc9923 84581e99d807 "nginx -g 'daemon of…" 2 hours ago Up 2 hours k8s_nginx-demonginx-demo_default_66958ef7-507a-41cd-a688-7a4976c6a71e_0 2fe0498ea9b5 k8s.gcr.io/pause:3.1 "/pause" 2 hours ago Up 2 hours k8s_POD_nginx-demo_default_66958ef7-507a-41cd-a688-7a4976c6a71e_0
3、查看docker容器详情信息
[root@node-3 ~]# docker container inspect 55d28fdc9923 [ ...部分输出省略... { "Image": "sha256:84581e99d807a703c9c03bd1a31cd9621815155ac72a7365fd02311264512656", "ResolvConfPath": "/var/lib/docker/containers/2fe0498ea9b5dfe1eb63eba09b1598a8dfd60ef046562525da4dcf7903a25250/resolv.conf", "HostConfig": { "Binds": [ "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/volumes/kubernetes.io~secret/default-token-5qwmc:/var/run/secrets/kubernetes.io/serviceaccount:ro", "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/etc-hosts:/etc/hosts", "/var/lib/kubelet/pods/66958ef7-507a-41cd-a688-7a4976c6a71e/containers/nginx-demo/1cc072ca:/dev/termination-log" ], "ContainerIDFile": "", "LogConfig": { "Type": "json-file", "Config": { "max-size": "100m" } }, "UTSMode": "", "UsernsMode": "", "ShmSize": 67108864, "Runtime": "runc", "ConsoleSize": [ 0, 0 ], "Isolation": "", "CpuShares": 256, CPU分配的权重，作用在requests.cpu上 "Memory": 268435456, 内存分配的大小，作用在limits.memory上 "NanoCpus": 0, "CgroupParent": "kubepods-burstable-pod66958ef7_507a_41cd_a688_7a4976c6a71e.slice", "BlkioWeight": 0, "BlkioWeightDevice": null, "BlkioDeviceReadBps": null, "BlkioDeviceWriteBps": null, "BlkioDeviceReadIOps": null, "BlkioDeviceWriteIOps": null, "CpuPeriod": 100000, CPU分配的使用比例，和CpuQuota一起作用在limits.cpu上 "CpuQuota": 50000, "CpuRealtimePeriod": 0, "CpuRealtimeRuntime": 0, "CpusetCpus": "", "CpusetMems": "", "Devices": [], "DeviceCgroupRules": null, "DiskQuota": 0, "KernelMemory": 0, "MemoryReservation": 0, "MemorySwap": 268435456, "MemorySwappiness": null, "OomKillDisable": false, "PidsLimit": 0, "Ulimits": null, "CpuCount": 0, "CpuPercent": 0, "IOMaximumIOps": 0, "IOMaximumBandwidth": 0, }, } ]
1.3. cpu资源测试
pod中cpu的限制主要通过requests.cpu和limits.cpu来定义，limits是不能超过的cpu大小，我们通过stress镜像来验证，stress是一个cpu和内存的压侧工具，通过指定args参数的定义压侧cpu的大小。监控pod的cpu和内存可通过kubectl top的方式来查看，依赖于监控组件如metric-server或promethus，当前没有安装，我们通过docker stats的方式来查看。
1、通过stress镜像定义一个pod，分配0.25个cores和最大限制0.5个core使用比例
[root@node-1 demo]# cat cpu-demo.yaml apiVersion: v1 kind: Pod metadata: name: cpu-demo namespace: default annotations: kubernetes.io/description: "demo for cpu requests and" spec: containers: - name: stress-cpu image: vish/stress resources: requests: cpu: 250m limits: cpu: 500m args: - -cpus - "1"
2、应用yaml文件生成pod
[root@node-1 demo]# kubectl apply -f cpu-demo.yaml pod/cpu-demo created
3、查看pod资源分配详情
[root@node-1 demo]# kubectl describe pods cpu-demo
Name: cpu-demo
Namespace: default
Priority: 0
Node: node-2/10.254.100.102
Start Time: Sat, 28 Sep 2019 14:33:12 +0800
Labels:
4、登陆到特定的node节点，通过docker container stats查看容器的资源使用详情
在pod所属的node上通过top查看，cpu的使用率限制百分比为50%。
通过上面的验证可以得出结论，我们在stress容器中定义使用1个core，通过limits.cpu限定可使用的cpu大小是500m，测试验证pod的资源已在容器内部或宿主机上都严格限制在50%（node机器上只有一个cpu，如果有2个cpu则会分摊为25%）。
1.4 memory资源测试
1、通过stress镜像测试验证requests.memory和limits.memory的生效范围，limits.memory定义容器可使用的内存资源大小，当超过内存设定的大小后容器会发生OOM，如下定义一个测试的容器，最大内存不能超过512M,使用stress镜像--vm-bytes定义压侧内存大小为256Mi
[root@node-1 demo]# cat memory-demo.yaml apiVersion: v1 kind: Pod metadata: name: memory-stress-demo annotations: kubernetes.io/description: "stress demo for memory limits" spec: containers: - name: memory-stress-limits image: polinux/stress resources: requests: memory: 128Mi limits: memory: 512Mi command: ["stress"] args: ["--vm", "1", "--vm-bytes", "256M", "--vm-hang", "1"]
2、应用yaml文件生成pod
[root@node-1 demo]# kubectl apply -f memory-demo.yaml
pod/memory-stress-demo created
[root@node-1 demo]# kubectl get pods memory-stress-demo -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
memory-stress-demo 1/1 Running 0 41s 10.244.1.19 node-2
3、查看资源的分配情况
[root@node-1 demo]# kubectl describe pods memory-stress-demo
Name: memory-stress-demo
Namespace: default
Priority: 0
Node: node-2/10.254.100.102
Start Time: Sat, 28 Sep 2019 15:13:06 +0800
Labels:
4、查看容器内存资源的使用情况，分配256M内存，最大可使用为512Mi，利用率为50%，此时没有超过limits限制的大小，容器运行正常
5、当容器内部超过内存的大小会怎么样呢，我们将--vm-byte设置为513M，容器会尝试运行，超过内存后会OOM，kube-controller-manager会不停的尝试重启容器,RESTARTS的次数会不停的增加。
[root@node-1 demo]# cat memory-demo.yaml apiVersion: v1 kind: Pod metadata: name: memory-stress-demo annotations: kubernetes.io/description: "stress demo for memory limits" spec: containers: - name: memory-stress-limits image: polinux/stress resources: requests: memory: 128Mi limits: memory: 512Mi command: ["stress"] args: ["--vm", "1", "--vm-bytes", "520M", "--vm-hang", "1"] . #容器中使用内存为520M 查看容器的状态为OOMKilled，RESTARTS的次数不断的增加，不停的尝试重启 [root@node-1 demo]# kubectl get pods memory-stress-demo NAME READY STATUS RESTARTS AGE memory-stress-demo 0/1 OOMKilled 3 60s
2. Pod服务质量
BestEffort 尽最大努力分配资源，默认没有指定resource分配的Qos，优先级最低； Burstable 可波动的资源，至少需要分配到requests中的资源，常见的QOS； Guaranteed 完全可保障资源，requests和limits定义的资源相同，优先级最高。
2.1 BestEffort最大努力
1、Pod中没有定义resource，默认的Qos策略为BestEffort,优先级别最低，当资源比较进展是需要驱逐evice时，优先驱逐BestEffort定义的Pod，如下定义一个BestEffort的Pod
[root@node-1 demo]# cat nginx-qos-besteffort.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-besteffort labels: name: nginx-qos-besteffort spec: containers: - name: nginx-qos-besteffort image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: {}
2、创建pod并查看Qos策略，qosClass为BestEffort
[root@node-1 demo]# kubectl apply -f nginx-qos-besteffort.yaml pod/nginx-qos-besteffort created 查看Qos策略 [root@node-1 demo]# kubectl get pods nginx-qos-besteffort -o yaml apiVersion: v1 kind: Pod metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-besteffort"},"name":"nginx-qos-besteffort","namespace":"default"},"spec":{"containers":[{"image":"nginx:1.7.9","imagePullPolicy":"IfNotPresent","name":"nginx-qos-besteffort","ports":[{"containerPort":80,"name":"nginx-port-80","protocol":"TCP"}],"resources":{}}]}} creationTimestamp: "2019-09-28T11:12:03Z" labels: name: nginx-qos-besteffort name: nginx-qos-besteffort namespace: default resourceVersion: "1802411" selfLink: /api/v1/namespaces/default/pods/nginx-qos-besteffort uid: 56e4a2d5-8645-485d-9362-fe76aad76e74 spec: containers: - image: nginx:1.7.9 imagePullPolicy: IfNotPresent name: nginx-qos-besteffort ports: - containerPort: 80 name: nginx-port-80 protocol: TCP resources: {} terminationMessagePath: /dev/termination-log ...省略... status: hostIP: 10.254.100.102 phase: Running podIP: 10.244.1.21 qosClass: BestEffort #Qos策略 startTime: "2019-09-28T11:12:03Z"
3、删除测试Pod
[root@node-1 demo]# kubectl delete pods nginx-qos-besteffort pod "nginx-qos-besteffort" deleted
2.2 Burstable可波动
1、Pod的服务质量为Burstable，仅次于Guaranteed的服务质量，至少需要一个container定义了requests，且requests定义的资源小于limits资源
[root@node-1 demo]# cat nginx-qos-burstable.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-burstable labels: name: nginx-qos-burstable spec: containers: - name: nginx-qos-burstable image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 100m memory: 128Mi limits: cpu: 200m memory: 256Mi
2、应用yaml文件生成pod并查看Qos类型
[root@node-1 demo]# kubectl apply -f nginx-qos-burstable.yaml
pod/nginx-qos-burstable created
查看Qos类型
[root@node-1 demo]# kubectl describe pods nginx-qos-burstable
Name: nginx-qos-burstable
Namespace: default
Priority: 0
Node: node-2/10.254.100.102
Start Time: Sat, 28 Sep 2019 19:27:37 +0800
Labels: name=nginx-qos-burstable
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-burstable"},"name":"nginx-qos-burstable","namespa...
Status: Running
IP: 10.244.1.22
Containers:
nginx-qos-burstable:
Container ID: docker://d1324b3953ba6e572bfc63244d4040fee047ed70138b5a4bad033899e818562f
Image: nginx:1.7.9
Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Sat, 28 Sep 2019 19:27:39 +0800
Ready: True
Restart Count: 0
Limits:
cpu: 200m
memory: 256Mi
Requests:
cpu: 100m
memory: 128Mi
Environment:
2.3 Guaranteed完全保障
1、resource中定义的cpu和memory必须包含有requests和limits，切requests和limits的值必须相同，其优先级别最高，当出现调度和驱逐时优先保障该类型的Qos,如下定义一个nginx-qos-guaranteed的容器，requests.cpu和limits.cpu相同，同理requests.memory和limits.memory.
[root@node-1 demo]# cat nginx-qos-guaranteed.yaml apiVersion: v1 kind: Pod metadata: name: nginx-qos-guaranteed labels: name: nginx-qos-guaranteed spec: containers: - name: nginx-qos-guaranteed image: nginx:1.7.9 imagePullPolicy: IfNotPresent ports: - name: nginx-port-80 protocol: TCP containerPort: 80 resources: requests: cpu: 200m memory: 256Mi limits: cpu: 200m memory: 256Mi
2、应用yaml文件生成pod并查看pod的Qos类型为可完全保障Guaranteed
[root@node-1 demo]# kubectl apply -f nginx-qos-guaranteed.yaml
pod/nginx-qos-guaranteed created
[root@node-1 demo]# kubectl describe pods nginx-qos-guaranteed
Name: nginx-qos-guaranteed
Namespace: default
Priority: 0
Node: node-2/10.254.100.102
Start Time: Sat, 28 Sep 2019 19:37:15 +0800
Labels: name=nginx-qos-guaranteed
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"nginx-qos-guaranteed"},"name":"nginx-qos-guaranteed","names...
Status: Running
IP: 10.244.1.23
Containers:
nginx-qos-guaranteed:
Container ID: docker://cf533e0e331f49db4e9effb0fbb9249834721f8dba369d281c8047542b9f032c
Image: nginx:1.7.9
Image ID: docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Sat, 28 Sep 2019 19:37:16 +0800
Ready: True
Restart Count: 0
Limits:
cpu: 200m
memory: 256Mi
Requests:
cpu: 200m
memory: 256Mi
Environment:
写在最后
本章是kubernetes系列教程第六篇文章，通过介绍resource资源的分配和服务质量Qos，关于resource有节点使用建议：
requests和limits资源定义推荐不超过1:2，避免分配过多资源而出现资源争抢，发生OOM； pod中默认没有定义resource，推荐给namespace定义一个limitrange，确保pod能分到资源； 防止node上资源过度而出现机器hang住或者OOM，建议node上设置保留和驱逐资源，如保留资源--system-reserved=cpu=200m,memory=1G，驱逐条件--eviction hard=memory.available<500Mi。
附录
容器计算资源管理：cpu资源管理：https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/
服务质量QOS：https://kubernetes.io/docs/tasks/configure-pod-container/quality-service-pod/
Docker关于CPU的限制：https://cnblogs.com/sparkdev/p/8052522.html
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