nfs v4.0协议下的服务器load升高问题

在使用nfs v4.0协议挂载nfs文件系统的时候，存在一个seq id序列号瓶颈问题，具体内容请看https://access.redhat.com/solutions/2142081

• There is a limitation to the Linux NFS4.0 client implementation that an "open_owner" is mapped to a userid. This results in a bottleneck if one user opens and closes a lot of files in a short period of time. Each OPEN / CLOSE operation has to wait for a sequence id, which essentially serializes each OPEN / CLOSE request. If an NFS server's response time for OPEN / CLOSE requests increases due to some secondary load or complication, this NFS4 client limitation can become pronounced, and in some cases, cause an unresponsive machine.
• The NFS4.1 protocol addresses the limitation of serialization of OPENs per open_owner. For more information, see RFC 5661 Section 9.10

故障时的现象：

服务器load无限升高，但是应用的cpu使用率并不高

故障触发条件：

短时间内read close大量的文件

解决的方案：

1. 使用nfs v3协议挂载规避

2. 使用nfs v4.1协议挂载

k8s pv的v3挂载实例：

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-test-pv
spec:
  accessModes:
  - ReadWriteMany
  capacity:
    storage: 1000Gi
  mountOptions:
  - vers=3
  - nolock
  - proto=tcp
  - noatime
  - nodiratime
  - noexec
  - hard
  - rsize=524288
  - wsize=524288
  nfs:
    path: /[nfs-id]/[mount-path]/
    server: [nfs-server-ip]
  persistentVolumeReclaimPolicy: Retain
  storageClassName: nfs-test-pv
  volumeMode: Filesystem
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-test-pvc
  namespace: default
spec:
  accessModes:
  - ReadWriteMany
  resources:
    requests:
      storage: 1000Gi
  storageClassName: nfs-test-pv
  volumeMode: Filesystem
  volumeName: nfs-test-pv