The task bmLink.0 is the Interface Management Task, If the number of interfaces are large, the link status of interface flaps, or the optical module is abnormal, the CPU usage of the task may increase.
If a non-Huawei certified optical module is used on the switch, the CPU usage may be high when the optical module is queried
https://support.huawei.com/enterprise/en/bulletins-product/ENEWS2000002116