Java performance tuning and troubleshooting
1. Introduction
When using Java to develop applications, it is inevitable to encounter performance problems of slow application speed. Performance issues can have a large impact on system stability, user experience, and application quality. Therefore, Java performance tuning has become particularly important.
2. Java performance bottleneck analysis and troubleshooting
Various possible causes of performance problems need to be considered when optimizing Java performance. Common causes of problems are as follows:
1. Performance problems caused by hardware reasons
Hardware reasons can be solved by upgrading hardware and optimizing hardware settings, or optimizing at the software level. For example, high-performance hardware should be selected when purchasing servers
2. Performance problems caused by JVM
JVM may have performance problems caused by various reasons. The common problems are as follows:
a. GC-related issues
The GC garbage collector may block the execution of the application, causing problems with application performance. The following strategies can be used to solve GC problems:
调整JVM参数优化GC算法，例如调整垃圾回收的频率或减少垃圾回收时间
按照业务场景调整堆大小
使用CMS、G1等更高级的垃圾回收器
b. Insufficient memory problem
Insufficient memory can lead to OOM, resulting in poor application performance. Use the following strategies to resolve out-of-memory issues:
检查代码中是否存在无用的对象，并尽快释放它们
可以使用-Xmx和-Xmn设置堆大小
c. CPU utilization is too high
The application consumes a lot of CPU resources, which may cause the overall system performance to decrease. The following strategies can be used to solve such problems:
打开JVM调优工具，检测什么导致CPU利用率过高优化代码
使用多线程来分摊CPU负荷
3. Performance issues caused by the application level
The application itself may have performance problems caused by various reasons, and the common problems are as follows:
a. Program algorithm complexity problem
The algorithmic complexity of the program needs to be evaluated and optimized to ensure that the application can still respond quickly when processing large amounts of data.
b. Too many database connections
A large number of database connections can also easily lead to system performance degradation, thereby affecting the performance of the application. The following strategies can be used to solve such problems:
使用数据库连接池来限制连接数量，避免连接过多
使用缓存技术减少数据库访问次数
c. Code BUG problems such as infinite loops
Bugs such as infinite loops or deadlocks in the code will also lead to system performance degradation. The following strategies can be used to solve such problems:
使用线程分析工具去检测
应用程序出现异常后及时释放资源，避免资源一直被占用
3. Java performance tuning plan formulation
1. Performance test plan
a. Stress test
Stress testing can simulate high concurrency and test a large number of concurrent requests on the target system. Get the system's maximum processing capacity, throughput, response time and other performance indicators.
b. Monitoring test
Monitoring and testing can detect system resource usage and understand system bottlenecks and resource allocation. Commonly used tools include JConsole, VisualVM, etc.
c. Diagnostic tests
Diagnostic tests can analyze system running status and diagnose system abnormalities and other problems. Common tools include jstack, jmap, jstat, hprof, etc.
2. Performance tuning plan formulation
a. JVM parameter adjustment
Improve system performance by adjusting JVM parameters to optimize garbage collection mechanism, adjust thread pool size, set program stack size, etc.
b. Code optimization
Optimizing the program code includes algorithm optimization, memory reuse, avoiding frequent IO, etc. to reduce program running time
c. Server environment optimization
Improve system performance by optimizing the operating system, hard disk, network and other environments.
3. Execute the tuning plan
a. Use of JVM tools
Use commonly used JVM tools such as Jconsole, VisualVM, Jstat, etc. to perform program diagnosis and tuning
b. Use of other tuning tools
Some specific scenarios can use other tuning tools, such as heap memory analysis tools, performance monitoring tools, etc.
4. Practical cases of Java performance tuning
1. Performance bottlenecks caused by GC
a. Case 1: Full GC occurs frequently
Reduce the frequency of Full GC by adjusting the proportion of young generation and old generation, increasing memory, reducing object size, etc.
b. Case 2: CMS GC cannot reclaim memory
Solve the problem that CMS GC cannot reclaim memory by increasing program pause time and reducing CMS GC execution time.
2. Performance bottlenecks caused by the application level
a. Case 1: Program algorithm complexity problem
Through algorithm improvement, data structure optimization, concurrent processing, etc., the operating efficiency of the program is improved.
b. Case 2: Performance problems caused by too many database connections
Reduce the number of database connections and optimize program performance by sorting out code logic, reusing objects, and increasing cache.
5. Summary and review
This article introduces the formulation, implementation and practical solutions of Java performance tuning solutions. From performance testing to performance tuning to performance problems in actual combat of Java programs.