java-performance

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Java Performance Skill

Java性能技能

Optimize JVM performance through profiling, GC tuning, and memory analysis.

通过性能剖析、GC调优和内存分析来优化JVM性能。

Overview

概述

This skill covers JVM performance optimization including garbage collection tuning, memory analysis, CPU profiling, and benchmarking with JMH.

本技能涵盖JVM性能优化相关内容，包括垃圾回收（GC）调优、内存分析、CPU性能剖析以及使用JMH进行基准测试。

When to Use This Skill

适用场景

Use when you need to:

Tune GC for low latency or throughput
Profile CPU hotspots
Analyze memory leaks
Benchmark code performance
Optimize container settings

当你需要以下操作时使用本技能：

针对低延迟或吞吐量进行GC调优
剖析CPU热点
分析内存泄漏
对代码性能进行基准测试
优化容器配置

Quick Reference

快速参考

GC Presets

GC预设配置

bash

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bash

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High-throughput

高吞吐量

-XX:+UseG1GC -XX:MaxGCPauseMillis=200 -Xms4g -Xmx4g -XX:+AlwaysPreTouch

Low-latency

低延迟

-XX:+UseZGC -XX:+ZGenerational -Xms8g -Xmx8g

Memory-constrained

内存受限场景

-XX:+UseSerialGC -Xms512m -Xmx512m -XX:+UseCompressedOops

Container-optimized

容器优化配置

-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0 -XX:+ExitOnOutOfMemoryError

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-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0 -XX:+ExitOnOutOfMemoryError

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Profiling Commands

性能剖析命令

bash

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bash

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Thread dump

线程转储

jstack -l <pid> > threaddump.txt

Heap dump

堆转储

jmap -dump:format=b,file=heap.hprof <pid>

GC analysis

GC分析

jstat -gcutil <pid> 1000 10

Flight recording

飞行记录

jcmd <pid> JFR.start duration=60s filename=app.jfr

Async profiler

异步性能剖析器

./profiler.sh -d 30 -f profile.html <pid>

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./profiler.sh -d 30 -f profile.html <pid>

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JMH Benchmark

JMH基准测试

java

@BenchmarkMode(Mode.Throughput)
@Warmup(iterations = 3, time = 1)
@Measurement(iterations = 5, time = 1)
@State(Scope.Benchmark)
public class MyBenchmark {

    @Benchmark
    public void testMethod(Blackhole bh) {
        bh.consume(compute());
    }
}

java

@BenchmarkMode(Mode.Throughput)
@Warmup(iterations = 3, time = 1)
@Measurement(iterations = 5, time = 1)
@State(Scope.Benchmark)
public class MyBenchmark {

    @Benchmark
    public void testMethod(Blackhole bh) {
        bh.consume(compute());
    }
}

GC Comparison

GC对比

GC	Latency	Throughput	Heap Size
G1	Medium	High	4-32GB
ZGC	Very Low	Medium	8GB-16TB
Shenandoah	Very Low	Medium	8GB+
Parallel	High	Very High	Any

GC	延迟	吞吐量	堆大小
G1	中等	高	4-32GB
ZGC	极低	中等	8GB-16TB
Shenandoah	极低	中等	8GB+
Parallel	高	极高	任意

Troubleshooting

故障排查

Problem	Cause	Solution
GC thrashing	Heap too small	Increase heap
High latency	GC pauses	Switch to ZGC
Memory leak	Object retention	Heap dump + MAT
CPU spikes	Hot loops	Profile + optimize

问题	原因	解决方案
GC抖动	堆内存过小	增大堆内存
高延迟	GC停顿	切换到ZGC
内存泄漏	对象被持续持有	堆转储 + MAT分析
CPU峰值	热点循环	性能剖析 + 优化

Usage

使用方式

Skill("java-performance")

Skill("java-performance")