What is the command to check Linux performance

1.uptime

#This command can quickly check the load status of the machine. In Linux systems, these data represent the number of processes waiting for CPU resources and blocked in uninterruptible IO processes (process status is D). This data can give us a macro understanding of system resource usage. The output of the

command indicates the average load conditions for 1 minute, 5 minutes, and 15 minutes respectively. Through these three data, you can understand whether the server load is becoming tight or easing in the area. If the 1-minute average load is very high and the 15-minute average load is very low, it means that the server is commanding a high load and you need to further investigate where the CPU resources are being consumed. On the other hand, if the 15-minute load average is high and the 1-minute load average is low, it is possible that the time when CPU resources are tight has passed. If the average load in the past minute is much higher than the load in 15 minutes, then we need to use the vmstat and mpstat commands to troubleshoot.

2.dmesg|tail

dmesgThis command is used to view boot information

dmesg|tailThis command will output the system log The last 10 lines of

3.vmstat1

Each line will output some core system indicators, which allow us to understand the system status in more detail. The following parameter 2 indicates that statistical information is output every two seconds. The header indicates the meaning of each column. These columns introduce some columns related to performance tuning:

r: Process waiting for CPU resources number. This data reflects the CPU load better than the average load. The data does not include processes waiting for IO. If this value is greater than the number of machine CPU cores, then the machine's CPU resources are saturated.

free: The amount of system available memory (in kilobytes). If the remaining memory is insufficient, it will also cause system performance problems. The free command introduced below can provide a more detailed understanding of system memory usage.

si,so: The number of writes and reads in the swap area. If this data is not 0, it means that the system is already using the swap area (swap) and the machine's physical memory is insufficient.

us,sy,id,wa,st: These all represent the consumption of CPU time. They respectively represent user time (user), system (kernel) time (sys), idle time (idle), IO Waiting time (wait) and stolen time (stolen, usually consumed by other virtual machines).

The above CPU times allow us to quickly understand whether the CPU is busy. Generally, if the sum of user time and system time is very large, the CPU is busy executing instructions. If the IO wait time is long, the bottleneck of the system may be disk IO.

4.mpstat-PALL1

#This command can display the occupancy of each CPU. If there is a CPU with a particularly high occupancy rate, it may be Caused by a single-threaded application.

5.pidstat1

The pidstat command outputs the CPU usage of the process. This command will continue to output and will not overwrite the previous data, making it easy to observe. System dynamics.

6.iostat-xz1

The iostat command is mainly used to check the machine disk IO status. The main meanings of the columns output by this command are:

r/s,w/s,rkB/s,wkB/s: respectively represent the number of reads and writes per second and the amount of data read and written per second (kilobytes) ). Excessive read and write volume may cause performance problems.

await: The average waiting time for IO operations, in milliseconds. This is the time the application needs to spend when interacting with the disk, including IO waiting and actual operation time. If this value is too large, the hardware device may have encountered a bottleneck or malfunctioned.

avgqu-sz: The average number of requests made to the device. If this value is greater than 1, the hardware device may be saturated (some front-end hardware devices support parallel writing).

%util: Device utilization. This value indicates how busy the device is. The empirical value is that if it exceeds 60, it may affect IO performance (you can refer to the average waiting time of IO operations). If it reaches 100%, it means that the hardware device is saturated.

If the data of the logical device is displayed, the device utilization does not mean that the actual back-end hardware device is saturated. It is worth noting that even if the IO performance is not ideal, it does not necessarily mean that the application performance will be poor. Strategies such as pre-reading and write caching can be used to improve application performance.

7.free-h

The free command can be used to view the system memory usage. The last two columns represent the amount of memory used for IO cache and the amount of memory used for file system page cache respectively. It should be noted that the second line -/buffers/cache, it seems that the cache takes up a lot of memory space. This is the memory usage strategy of the Linux system. Utilize the memory as much as possible. If the application needs memory, this memory will be immediately reclaimed and allocated to the application. Therefore, this part of memory is generally regarded as available memory.

If there is very little available memory, the system may use the swap area (if configured), which will increase IO overhead (can be withdrawn in the iostat command) and reduce system performance.

8.sar-nDEV1

The sar command can check the throughput rate of the network device here. When troubleshooting performance problems, you can judge whether the network device is saturated by the throughput of the network device. As shown in the sample output, the throughput rate of the eth0 network card device is only about 0.39Mbytes/s.

9.sar-nTCP,ETCP1

The sar command is in This is used to view the TCP connection status, including:

active/s: the number of locally initiated TCP connections per second, that is, the TCP connections created through the connect call;

passive/s: every The number of remotely initiated TCP connections per second, that is, the TCP connections created through the accept call;

retrans/s: the number of TCP retransmissions per second;

The number of TCP connections can be used to determine whether there is a performance problem Since too many connections have been established, it can be further determined whether the connection is actively initiated or passively accepted. TCP retransmission may be caused by poor network environment or excessive server pressure, resulting in packet loss.

10.top

The first line is the task queue information, which is the same as the execution result of the uptime command: the first column represents the current time, the second column Indicates how long the system has been running, the third column indicates the current number of people logged in, and the last loadaverage indicates the system load (the three values ​​are: 1 minute, 5 minutes, and 15 minutes ago to the present load average)

The second column represents the process information, which is very intuitive.

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