背景

现在有些场景下，SCSI协议会过网络，导致性能很低

SCSI 读请求

sequenceDiagram
    VM->>VMM: cbw_req
    VMM->>HOST: net
    HOST->>DEV: cbw_req
    DEV-->>HOST:cbw_rsp
    HOST-->>VMM: net
    VMM-->>VM: cbw_req

    VM->>VMM: data_req
    VMM->>HOST: net
    HOST->>DEV: data_req
    activate DEV
    DEV-->>HOST: data_rsp
    deactivate DEV
    HOST-->>VMM: net
    VMM-->>VM: data_rsp
    activate VM

    VM->>VMM: csw_req
    deactivate VM
    VMM->>HOST: net
    HOST->>DEV: csw_req
    DEV-->>HOST:csw_rsp
    HOST-->>VMM: net
    VMM-->>VM: csw_rsp

• 主要性能消耗：
  • 1、6次net通信
  • 2、DEV处理date读请求
  • 3、data返回那次通信
  • 4、VM处理data返回

SCSI 读请求优化

sequenceDiagram
    VM->>VMM: cbw_req
    VMM->>HOST: net
    VMM-->>VM: cbw_rsp
    HOST->>DEV: cbw_req
    DEV-->>HOST: cbw_rsp
    HOST->>DEV: data1_req
    activate DEV
    DEV-->>HOST: data1_rsp
    deactivate DEV
    activate HOST
    HOST->>DEV: data2_req
    HOST-->>VMM: data1_rsp_net
    deactivate HOST
    DEV-->>HOST: data2_rsp
    activate HOST
    HOST-->>VMM: data2_rsp_net
    HOST-->>VMM: datan_rsp_net

    VM->>VMM: data_req
    VMM-->>VM: data_rsp
    VM->>VMM: csw_req
    VMM->>VM: csw_rsp

    HOST->>DEV: csw_req
    deactivate HOST
    DEV-->>HOST: csw_rsp