探索JVM运行状态的利器—JVMPI，HPROF_剑_百度空间 (引)
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．什么是JVMPI？Java Virtual Machine Profiler Interface。参考 JVMPI可以做什么？它可以监控VM发生的各种事件。例如当JVM创建，关闭，Java类被加载，创建对象，或GC回收，等37种事件。既然是接口自然就是有一个头文件，[JAVA_HOME]\include\jvmpi.h。您可以开发自己的Profiler监控Java VM的发生的各种事件。
下面是我编写的使用JVMPI的例子，输出结果说明了为了运行一个Java类，JVM需要做的各种操作。
#include <jvmpi.h> //1.>cl -LDd -Zi -I. -IC:\j2sdk1.4.2_10\include -IC // :\j2sdk1.4.2_10\include\win32 -Tp.\jvmtrace.c -o jvmtrace.dll //2.>copy jvmtrace.dll C:\j2sdk1.4.2_10\bin\ //3.>java -Xrunjvmtrace org.colimas.jni.test.JniTest //jvmpi interface 全局指针 static JVMPI_Interface *jvmpi_interface; //时间通知处理函数 void notifyEvent(JVMPI_Event *event) { switch(event->event_type) { /*非常可怕的输出，好奇就试试。 case JVMPI_EVENT_CLASS_LOAD: fprintf(stderr, "trace> Class Load : %s\n", event->u.class_load.class_name); break;*/ case JVMPI_EVENT_ARENA_DELETE : fprintf(stderr, "trace> The heap arena :%d is deleted.\n", event->u.delete_arena.arena_id); break; case JVMPI_EVENT_ARENA_NEW : fprintf(stderr, "trace> The heap arena %s:%d is created.\n", event->u.new_arena.arena_name, event->u.new_arena.arena_id); break; case JVMPI_EVENT_GC_FINISH : fprintf(stderr, "trace> GC is finished. Used object:%d, space:%d, total object space:%d.\n", event->u.gc_info.used_objects, event->u.gc_info.used_object_space, event->u.gc_info.total_object_space); break; case JVMPI_EVENT_GC_START : fprintf(stderr, "trace>GC is started.\n"); break; case JVMPI_EVENT_HEAP_DUMP : fprintf(stderr, "trace> The heap dump begin %s,end %s.\n", event->u.heap_dump.begin, event->u.heap_dump.end); break; case JVMPI_EVENT_JVM_INIT_DONE : fprintf(stderr, "trace> JVM initialization is done.\n"); break; case JVMPI_EVENT_JVM_SHUT_DOWN : fprintf(stderr, "trace> JVM is shutting down.\n"); break; case JVMPI_EVENT_THREAD_END : fprintf(stderr, "trace> A thread ends.\n"); break; case JVMPI_EVENT_THREAD_START : fprintf(stderr, "trace> The thread %s begins whose group is %s, parent is %s.\n", event->u.thread_start.thread_name , event->u.thread_start.group_name, event->u.thread_start.parent_name); break; } } // profiler agent entry point extern "C" { JNIEXPORT jint JNICALL JVM_OnLoad(JavaVM *jvm, char *options, void *reserved) { fprintf(stderr, "trace> initializing ..... \n");
// get jvmpi interface pointer if ((jvm->GetEnv((void **)&jvmpi_interface, JVMPI_VERSION_1)) < 0) { fprintf(stderr, "trace> error in obtaining jvmpi interface pointer\n"); return JNI_ERR; } // initialize jvmpi interface jvmpi_interface->NotifyEvent = notifyEvent; // enabling class load event notification //jvmpi_interface->EnableEvent(JVMPI_EVENT_CLASS_LOAD, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_ARENA_DELETE, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_ARENA_NEW, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_GC_FINISH, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_GC_START, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_HEAP_DUMP, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_JVM_INIT_DONE, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_JVM_SHUT_DOWN, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_THREAD_END, NULL); jvmpi_interface->EnableEvent(JVMPI_EVENT_THREAD_START, NULL); fprintf(stderr, "trace> .... ok, dumping...\n"); if (jvmpi_interface->RequestEvent(JVMPI_EVENT_HEAP_DUMP,NULL)<0) { fprintf(stderr, "trace> error in obtaining jvmpi interface pointer\n"); return JNI_ERR; } fprintf(stderr, "trace> .... end\n\n"); return JNI_OK; } } 编译 >cl -LDd -Zi -I. -IC:\j2sdk1.4.2_10\include -IC :\j2sdk1.4.2_10\include\win32 -Tp.\jvmtrace.c -o jvmtrace.dll 拷贝jvmtrace.dll到JAVA_HOME\bin >copy jvmtrace.dll C:\j2sdk1.4.2_10\bin\ 运行 >java -Xrunjvmtrace org.colimas.jni.test.JniTest 结果 trace> initializing ..... trace> .... ok, dumping... trace> .... end trace> The thread Finalizer begins whose group is system, parent is (null). trace> The thread Reference Handler begins whose group is system, parent is (nul l). trace> The thread main begins whose group is main, parent is system. trace> JVM initialization is done. trace> The thread Signal Dispatcher begins whose group is system, parent is (nul l). hello JVM trace> A thread ends. trace> The thread DestroyJavaVM begins whose group is main, parent is system. trace> A thread ends. trace> JVM is shutting down. 2．HPROF又什么是？HPROF是J2SE自带的一个简单的profiler agent。 他是一个动态链接库文件，监控CPU的使用率，Heap分配情况等。将这些信息输出到文件或到socket。 java –Xrunhprof ToBeProfiledClass [:help]|[:=, ...] 例如： >java -Xrunhprof:heap=all org.colimas.jni.test.JniTest 在当前目录会生成java.hprof.txt文件。文件内记载了JVM运行时Heap的运行情况。 |