Hello Steelbule,
You can use the car command to set the rate limit for packets sent to the CPU.
https://support.huawei.com/hedex/hdx.do?docid=EDOC1100101074&id=EN-US_CLIREF_0177117962&lang=en
For your case, the configuration is as follows:
[Huawei]cpu-defend policy test1
[Huawei-cpu-defend-policy-test1]car packet-type snmp cir 256 cbs30000
[Huawei ] cpu-defend policytest1 globally