JVM调优基础到进阶 (5)

▪https://www.oracle.com/technical-resources/articles/java/g1gc.html

G1日志详解 [GC pause (G1 Evacuation Pause) (young) (initial-mark), 0.0015790 secs] //young -> 年轻代 Evacuation-> 复制存活对象 //initial-mark 混合回收的阶段，这里是YGC混合老年代回收 [Parallel Time: 1.5 ms, GC Workers: 1] //一个GC线程 [GC Worker Start (ms): 92635.7] [Ext Root Scanning (ms): 1.1] [Update RS (ms): 0.0] [Processed Buffers: 1] [Scan RS (ms): 0.0] [Code Root Scanning (ms): 0.0] [Object Copy (ms): 0.1] [Termination (ms): 0.0] [Termination Attempts: 1] [GC Worker Other (ms): 0.0] [GC Worker Total (ms): 1.2] [GC Worker End (ms): 92636.9] [Code Root Fixup: 0.0 ms] [Code Root Purge: 0.0 ms] [Clear CT: 0.0 ms] [Other: 0.1 ms] [Choose CSet: 0.0 ms] [Ref Proc: 0.0 ms] [Ref Enq: 0.0 ms] [Redirty Cards: 0.0 ms] [Humongous Register: 0.0 ms] [Humongous Reclaim: 0.0 ms] [Free CSet: 0.0 ms] [Eden: 0.0B(1024.0K)->0.0B(1024.0K) Survivors: 0.0B->0.0B Heap: 18.8M(20.0M)->18.8M(20.0M)] [Times: user=0.00 sys=0.00, real=0.00 secs] //以下是混合回收其他阶段 [GC concurrent-root-region-scan-start] [GC concurrent-root-region-scan-end, 0.0000078 secs] [GC concurrent-mark-start] //无法evacuation，进行FGC [Full GC (Allocation Failure) 18M->18M(20M), 0.0719656 secs] [Eden: 0.0B(1024.0K)->0.0B(1024.0K) Survivors: 0.0B->0.0B Heap: 18.8M(20.0M)->18.8M(20.0M)], [Metaspace: 38 76K->3876K(1056768K)] [Times: user=0.07 sys=0.00, real=0.07 secs] 案例汇总

OOM产生的原因多种多样，有些程序未必产生OOM，不断FGC(CPU飙高，但内存回收特别少) （上面案例）

硬件升级系统反而卡顿的问题（见上）

线程池不当运用产生OOM问题（见上）
不断的往List里加对象（实在太LOW）

smile jira问题
实际系统不断重启
解决问题 加内存 + 更换垃圾回收器 G1
真正问题在哪儿？不知道

tomcat http-header-size过大问题（Hector）

lambda表达式导致方法区溢出问题(MethodArea / Perm Metaspace)
LambdaGC.java -XX:MaxMetaspaceSize=9M -XX:+PrintGCDetails

"C:\Program Files\Java\jdk1.8.0_181\bin\java.exe" -XX:MaxMetaspaceSize=9M -XX:+PrintGCDetails "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.1\lib\idea_rt.jar=49316:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_181\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_181\jre\lib\rt.jar;C:\work\ijprojects\JVM\out\production\JVM;C:\work\ijprojects\ObjectSize\out\artifacts\ObjectSize_jar\ObjectSize.jar" com.mashibing.jvm.gc.LambdaGC [GC (Metadata GC Threshold) [PSYoungGen: 11341K->1880K(38400K)] 11341K->1888K(125952K), 0.0022190 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] [Full GC (Metadata GC Threshold) [PSYoungGen: 1880K->0K(38400K)] [ParOldGen: 8K->1777K(35328K)] 1888K->1777K(73728K), [Metaspace: 8164K->8164K(1056768K)], 0.0100681 secs] [Times: user=0.02 sys=0.00, real=0.01 secs] [GC (Last ditch collection) [PSYoungGen: 0K->0K(38400K)] 1777K->1777K(73728K), 0.0005698 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] [Full GC (Last ditch collection) [PSYoungGen: 0K->0K(38400K)] [ParOldGen: 1777K->1629K(67584K)] 1777K->1629K(105984K), [Metaspace: 8164K->8156K(1056768K)], 0.0124299 secs] [Times: user=0.06 sys=0.00, real=0.01 secs] java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:388) at sun.instrument.InstrumentationImpl.loadClassAndCallAgentmain(InstrumentationImpl.java:411) Caused by: java.lang.OutOfMemoryError: Compressed class space at sun.misc.Unsafe.defineClass(Native Method) at sun.reflect.ClassDefiner.defineClass(ClassDefiner.java:63) at sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:399) at sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:394) at java.security.AccessController.doPrivileged(Native Method) at sun.reflect.MethodAccessorGenerator.generate(MethodAccessorGenerator.java:393) at sun.reflect.MethodAccessorGenerator.generateSerializationConstructor(MethodAccessorGenerator.java:112) at sun.reflect.ReflectionFactory.generateConstructor(ReflectionFactory.java:398) at sun.reflect.ReflectionFactory.newConstructorForSerialization(ReflectionFactory.java:360) at java.io.ObjectStreamClass.getSerializableConstructor(ObjectStreamClass.java:1574) at java.io.ObjectStreamClass.access$1500(ObjectStreamClass.java:79) at java.io.ObjectStreamClass$3.run(ObjectStreamClass.java:519) at java.io.ObjectStreamClass$3.run(ObjectStreamClass.java:494) at java.security.AccessController.doPrivileged(Native Method) at java.io.ObjectStreamClass.<init>(ObjectStreamClass.java:494) at java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:391) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1134) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348) at javax.management.remote.rmi.RMIConnectorServer.encodeJRMPStub(RMIConnectorServer.java:727) at javax.management.remote.rmi.RMIConnectorServer.encodeStub(RMIConnectorServer.java:719) at javax.management.remote.rmi.RMIConnectorServer.encodeStubInAddress(RMIConnectorServer.java:690) at javax.management.remote.rmi.RMIConnectorServer.start(RMIConnectorServer.java:439) at sun.management.jmxremote.ConnectorBootstrap.startLocalConnectorServer(ConnectorBootstrap.java:550) at sun.management.Agent.startLocalManagementAgent(Agent.java:137)

直接内存溢出问题（少见）
《深入理解Java虚拟机》P59，使用Unsafe分配直接内存，或者使用NIO的问题

栈溢出问题
-Xss设定太小