jdk6 OperatingSystemMXBean.TotalPhysicalMemorySize windows2003下得不到真实的内存值（大于2G）...-优快云博客

本文提供了解决JDK6版本中在Windows 2003环境下无法正确获取内存值的问题的方法，通过JNI重写相关函数来获取真实内存大小。

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jdk6中 OperatingSystemMXBean.TotalPhysicalMemorySize， windows2003下得不到真实的内存值（大于2G），这个BUG已经被修改在新的版本中
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6853676，
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6628662
如果你不想升级JDK而且又必须使用这个几个函数的话，可以使用JNI的方法重写这个几个函数
JNIEXPORT jlong JNICALL
Java_com_sun_management_OperatingSystem_getTotalSwapSpaceSize
(JNIEnv *env, jobject mbean)
{
- MEMORYSTATUS ms;
- GlobalMemoryStatus(&ms);
- return (jlong)ms.dwTotalPageFile;
+ MEMORYSTATUSEX ms;
+ ms.dwLength = sizeof(ms);
+ GlobalMemoryStatusEx(&ms);
+ return (jlong) ms.ullTotalPageFile;
}

JNIEXPORT jlong JNICALL
Java_com_sun_management_OperatingSystem_getFreeSwapSpaceSize
(JNIEnv *env, jobject mbean)
{
- MEMORYSTATUS ms;
- GlobalMemoryStatus(&ms);
- return (jlong)ms.dwAvailPageFile;
+ MEMORYSTATUSEX ms;
+ ms.dwLength = sizeof(ms);
+ GlobalMemoryStatusEx(&ms);
+ return (jlong) ms.ullAvailPageFile;
}

JNIEXPORT jlong JNICALL
Java_com_sun_management_OperatingSystem_getFreePhysicalMemorySize
(JNIEnv *env, jobject mbean)
{
- MEMORYSTATUS ms;
- GlobalMemoryStatus(&ms);
- return (jlong) ms.dwAvailPhys;
+ MEMORYSTATUSEX ms;
+ ms.dwLength = sizeof(ms);
+ GlobalMemoryStatusEx(&ms);
+ return (jlong) ms.ullAvailPhys;
}

JNIEXPORT jlong JNICALL
Java_com_sun_management_OperatingSystem_getTotalPhysicalMemorySize
(JNIEnv *env, jobject mbean)
{
- MEMORYSTATUS ms;
- // also returns dwAvailPhys (free physical memory bytes),
- // dwTotalVirtual, dwAvailVirtual,
+ MEMORYSTATUSEX ms;
+ ms.dwLength = sizeof(ms);
+ // also returns ullAvailPhys (free physical memory bytes),
+ // ullTotalVirtual, ullAvailVirtual,
// dwMemoryLoad (% of memory in use)
- GlobalMemoryStatus(&ms);
- return ms.dwTotalPhys;
+ GlobalMemoryStatusEx(&ms);
+ return (jlong) ms.ullTotalPhys;
}