Common reasons for slowing Linux servers include resource bottlenecks, improper configuration, or excessive background process usage. 1. First check the CPU and memory usage, use the top/htop command to see if there is a high process occupancy, combine free -h to determine whether the memory is insufficient, and pay attention to issues such as web server concurrency and unoptimized database queries; 2. Then check the disk IO performance, use iostat/iotop to see if the disk %util is close to 100%, identify frequently read and write programs such as database logs, and consider upgrading SSD or optimizing queries; 3. Then check the network delay and number of connections, use ping/traceroute to test network delay, observe the connection status through netstat/ss, and optimize HTTP request processing and TCP parameters; 4. Finally, check the timing tasks and background processes, check the crontab/systemctl timesers to confirm whether there are scripts that have been executed too long, adjust the task time, priority and resource limitations to reduce the impact.

There are many reasons why Linux servers are slowing down, common ones include resource bottlenecks, improper configuration or excessive background process usage. If you find that the server responds slowly and the loading time becomes longer, you can first start with the use of system resources.

1. Check CPU and memory usage

The most direct way is to use top or more intuitive htop command to view the current system's resource usage. If the CPU usage rate is close to 100% for a long time, or the memory is almost exhausted, it means that a program is consuming a lot of resources.

• Use the command: top or htop (need to install)
• Check whether a process occupies high CPU or memory for a long time
• If the memory is insufficient, you can combine free -h to view the total amount of available memory

Frequently asked questions include:

• Too many concurrent requests on web servers (such as Nginx/Apache)
• Database query is not optimized, causing load to rise
• Background scripts or timing tasks are frequently executed

It is recommended to monitor resource usage trends regularly, such as using sar or vmstat tools to record historical data to help determine whether it is a burst load or a persistent problem.

2. Check whether disk IO has become a bottleneck

Even if the CPU and memory look normal, disk read and write can slow down the entire system. Especially when using traditional mechanical hard disks, large amounts of IO operations can lead to a significant increase in latency.

You can use the following command to view disk performance:

• iostat -x 1 (Sysstat needs to be installed)
• iotop (similar to top, but for IO)

If you see that %util of a disk is close to 100% for a long time, it means that it is running at full capacity. At this time, you should see which programs are frequently reading and writing to disks, such as database logs, temporary file generation, backup tasks, etc.

Solutions include:

• Upgrade to SSD
• Optimize database queries to reduce unnecessary writes
• Mount log or cache directory to a separate disk partition

3. Check network latency and connection count

Sometimes the server itself runs normally, but network problems can also make you feel that "the server is very slow". For example, DNS resolution is slow, backend API response is delayed, or high latency between the client and the server.

Commonly used troubleshooting methods:

• Check network connectivity and latency using ping and traceroute
• Use netstat -antp or ss -antp to view the current connection status
• Observe whether there are a large number of TIME_WAIT or CLOSE_WAIT connections, it may be that the program has not handled the connection release well.

Common problems in web services are:

• HTTP requests accumulate, connection not released in time
• The backend calls the third-party interface timed out, causing blockage
• SSL handshake process is slow, especially if older versions of OpenSSL or configuration is unreasonable

It is recommended to adjust the TCP parameters appropriately, such as increasing the connection queue, shortening the TIME_WAIT time, and optimizing the application logic to avoid serial waiting.

4. Don't ignore regular tasks and background processes

In many cases, the sudden slowdown of the server occurs in the early hours of every day or in other fixed time periods, which is often because the crontab timing task initiates a large number of calculations or backup operations.

Inspection method:

• View the current timing task: crontab -l
• View system-level tasks: systemctl list-timers

If you find that a script is executed for too long or does not limit the number of concurrency, it will cause temporary lag. Consider:

• Stagger the execution time of multiple timing tasks
• Set nice/renice priority to reduce the impact on the main thread
• Add resource limits to scripts, such as maximum memory or CPU usage time

Basically, these common investigation directions. Server slowing down is not necessarily caused by one reason, but is often the result of the superposition of multiple factors. Starting from the use of resources and gradually deepening, you can find the problem.

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