Procedure
- Run the display cpu-usage command to obtain the tasks that cause high CPU usage. Pay special attention to the top 3 tasks with the highest CPU usage. In V200R005 and later versions, task names (specified by TaskName) in the command output are displayed in the descending order of CPU usage.
The following table lists the common tasks that cause high CPU usage, and reasons and solutions to lower CPU usage.
Table 1 Common tasks that cause high CPU usage and solutions Task
Category
Cause
Solution
VIDL
System idle task
A larger value for this task indicates a lower CPU usage.
A switch uses how long the VIDL task is using the CPU to calculate its CPU usage. No action is required.
BOX/INFO
Information center management tasks
When a switch outputs a huge amount of debugging or log information, the CPU usage of these tasks is high
Disable the debugging or logging function.
Analyze the generated debugging or log information and delete their trigger conditions.
DEV/HOTT/FMCK/SRMT/SRMI
Switch management tasks
During configuration restoration, active/standby MPU switchovers, and card insertion, the CPU usage of these tasks may rise for a short time. This is a normal phenomenon.
If many interrupts are reported due to some hardware faults, the CPU usage of these tasks also rises abnormally.
IFNT/IFPD/bmLINK
Interface management tasks
If there are many interfaces, the link protocol status of interfaces flaps, or optical modules are abnormal, the CPU usage of these tasks may rise.
Check whether interfaces and optical modules are working properly.
Specifically, check whether an interface frequently alternates between Up and Down according to log or alarm information. If an interface frequently flaps, check whether the optical module of the interface is faulty or a non-Huawei-certified optical module is used. For details, see Optical Interface Interconnection Is Abnormal on CE Switches. Additionally, analyze the configuration and traffic volume of the interface.
IPCR/IPCQ/RPCQ
Inter-switch or inter-card communication tasks.
If a large number of inter-switch or inter-card management messages are generated in scenarios such as where many routes or a ring network flaps and many users go online simultaneously, the CPU usage of these tasks may rise.
Checking Whether Network Flappings Exist or Checking Whether High CPU Usage Is Caused by a Hardware Failure
L3I4
Interface cards deliver IPv4 unicast forwarding entries.
Route flappings cause the CPU usage of this task to rise.
bcmL2MOD.0
MAC entry task
Checking Whether High CPU Usage Is Caused by a Hardware Failure
MSYN
MAC management task
Network loops cause the CPU usage of this task to rise.
Checking Whether High CPU Usage Is Caused by a Hardware Failure
AGNT
IPv4 SNMP protocol stack task
Frequent NMS operations cause the NMS to fail to deliver its requests within the due time. As a result, the CPU usage of this task rises.
Analyze the cause with a reference to network management events. If necessary, reduce NMS request frequency or block NMS requests.
AGT6
IPv6 SNMP protocol stack task
Frequent NMS operations cause the NMS to fail to deliver its requests within the due time. As a result, the CPU usage of this task rises.
Analyze the cause with a reference to network management events. If necessary, reduce NMS request frequency or block NMS requests.
VTx
Virtual terminal task
If management user terminals generate a large amount of data or management users run time-consuming commands, the CPU usage of this task may rise.
If management users' operations are proper and do not affect services, no action is required.
If CPU usage is continuously high or services are affected, collect information and seek technical support.
FTPS/FCx
Provide the FTP server function.
If multiple FTP connections simultaneously transmit files at a high speed, the CPU usage of these tasks may rise.
Do not use multiple FTP connections to simultaneously transmit files.
Limit the rate at which FTP clients transmit files to the switch functioning as an FTP server.
bcmRx/bcmT/FTS/FBUF/VP/VPR/VPS/SOCK
Packet sending and receiving tasks
If a large number of protocol packets are sent to the CPU, the CPU usage of these tasks significantly rises.
Usually, this is the most important reason for high CPU usage.
The causes are:
The CPU is under attack.
Network loops occur.
Service traffic is heavy.
Checking Whether Network Attacks Exist or Checking Whether High CPU Usage Is Caused by a Hardware Failure
DHCP
Implements DHCP protocol stack processing and completes DHCP snooping and DHCP relay.
The CPU is under attack by DHCP protocol packets.
NOTE:
x in the tasks indicates the sequence in which users log in.
The preceding table roughly tells the causes of high CPU usage. For specific causes and solutions, proceed with the next steps.