If you find that the server is running slowly or the memory usage is too high, you should check the cause before operating. First, you need to check the system resource usage, use top, htop, free -h, iostat, ss -antp and other commands to check the CPU, memory, disk I/O and network connections; secondly, analyze specific process problems, and track the behavior of high-occupancy processes through tools such as ps, jstack, strace; then check logs and monitoring data, view OOM records, exception requests, slow queries and other clues; finally, targeted processing is carried out based on common reasons such as memory leaks, connection pool exhaustion, cache failure storms, and timing task conflicts, optimize code logic, set up a timeout retry mechanism, add current limit fuses, and regularly pressure measurement and evaluation resources.

If you find that the server is running slowly or the memory usage is too high, don't rush to restart. Find out what the problem is first, otherwise you will make it again next time. This type of problem is usually related to resource usage, process exceptions or configuration errors.

Here are some common troubleshooting directions and practical suggestions:

Check system resource usage

First of all, you must know the load and resource consumption of the current system. Commonly used commands include top , htop (more intuitive), free -h and vmstat .

• CPU usage : Use top or htop to see which process occupies a large amount of CPU.
• Memory usage : free -h can quickly view total memory, used memory and cache.
• Disk I/O : Use iostat or iotop to check whether there are processes that frequently read and write to the disk.
• Network connection : netstat -antp or ss -antp can tell whether there is an abnormal connection or port occupancy.

If a process suddenly soars the resource, you can first record its PID and analyze it further later.

Analyze specific process issues

After finding a process that occupies high resources, the next step is to see what it is doing. For example, a Java application may cause frequent lag due to Full GC; while a PHP-FPM process may result in dead loops or slow queries in the code.

You can use the following methods to analyze in depth:

• Use ps -p <pid></pid> to view basic information of the process
• For Java applications, you can use jstack <pid></pid> to grab the thread stack to see if it is stuck somewhere
• Use strace -p <pid></pid> to see which system calls the process and whether there are long-term blocking operations
• If it is a database-related service, such as MySQL, check the slow query log to see if there is no unoptimized SQL

Sometimes you will find that although a certain process occupies a high amount, it is actually normal behavior, such as during the execution of the backup task. So we need to look at it in combination with business logic.

Check logs and monitor data

Logs are often the key clue to discovering problems. System logs (such as /var/log/messages or journalctl ), application logs, and database logs must be viewed.

• Is there a record of OOM (Out of Memory) being killed? You can view it through dmesg | grep -i kill
• Are there any abnormal requests, timeouts, retry and other phenomena in the application log?
• Are there any slow query, lock waiting and other situations in the database log?

If there is a monitoring system (such as Prometheus Grafana), it will be easier to see the trend. For example, does memory use continue to rise? Are there any timed tasks that trigger a large number of operations at a specific point in time?

Common Causes and Treatment Suggestions

Some problems are actually quite common, such as:

• Memory Leaks : Programs written in certain languages ??(such as Node.js, Java) are prone to memory leaks, and you can use corresponding tools to analyze heap memory snapshots.
• Connection pool exhaustion : The database connection is not released and the HTTP request is not set timeout may cause accumulation.
• Cache failure storm : After the cache is invalidated on a large scale, all requests are hit to the database, causing an avalanche.
• Timed task conflict : multiple tasks run at the same time, eating up all resources.

When encountering these problems, you can start from these aspects:

• Optimize code logic to reduce unnecessary resource usage
• Set a reasonable timeout and retry mechanism
• Add current limit and fuse to key interfaces
• Regular performance stress testing and resource assessment

Basically that's it. When the server slows down or the memory is exploded, first look at the overall resources, then locate the specific process, then check the logs and monitoring, and finally make judgments based on common patterns. Not every time, expert knowledge is required, but there is a lot of attention to details, especially those that "look normal but are actually problematic".

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