我认为我在NetBeans中将堆大小增加到1 GB,因为我将配置更改为如下所示:
netbeans_default_options="-J-Xmx1g ......
重新启动NetBeans之后,可以确定现在给我的应用程序1 GB了吗?
有没有办法验证这一点?
使用此代码:
// Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase // after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
对我来说很有用。
public class CheckHeapSize {
public static void main(String[] args) {
// TODO Auto-generated method stub
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase // after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
System.out.println("heapsize"+formatSize(heapSize));
System.out.println("heapmaxsize"+formatSize(heapMaxSize));
System.out.println("heapFreesize"+formatSize(heapFreeSize));
}
public static String formatSize(long v) {
if (v < 1024) return v + " B";
int z = (63 - Long.numberOfLeadingZeros(v)) / 10;
return String.format("%.1f %sB", (double)v / (1L << (z*10)), " KMGTPE".charAt(z));
}
}
您可以使用jconsole(大多数JDK的标准配置)来检查任何Java进程的堆大小。
与Sun Java 6 JDK的jvisualvm附接。列出了启动标志。
您可以使用该工具:Eclipse Memory Analyzer Tool http://www.eclipse.org/mat/。
非常有用。
当jvisualvm过大或您仅需要CLI时的个人收藏夹:jvmtop
JvmTop 0.8.0 alpha amd64 8 cpus, Linux 2.6.32-27, load avg 0.12
https://github.com/patric-r/jvmtop
PID MAIN-CLASS HPCUR HPMAX NHCUR NHMAX CPU GC VM USERNAME #T DL
3370 rapperSimpleApp 165m 455m 109m 176m 0.12% 0.00% S6U37 web 21
11272 ver.resin.Resin [ERROR: Could not attach to VM]
27338 WatchdogManager 11m 28m 23m 130m 0.00% 0.00% S6U37 web 31
19187 m.jvmtop.JvmTop 20m 3544m 13m 130m 0.93% 0.47% S6U37 web 20
16733 artup.Bootstrap 159m 455m 166m 304m 0.12% 0.00% S6U37 web 46
您可以通过MXBeans完成
public class Check {
public static void main(String[] args) {
MemoryMXBean memBean = ManagementFactory.getMemoryMXBean() ;
MemoryUsage heapMemoryUsage = memBean.getHeapMemoryUsage();
System.out.println(heapMemoryUsage.getMax()); // max memory allowed for jvm -Xmx flag (-1 if isn't specified)
System.out.println(heapMemoryUsage.getCommitted()); // given memory to JVM by OS ( may fail to reach getMax, if there isn't more memory)
System.out.println(heapMemoryUsage.getUsed()); // used now by your heap
System.out.println(heapMemoryUsage.getInit()); // -Xms flag
// |------------------ max ------------------------| allowed to be taken by you from OS
// |------------------ committed -------| | now taken from OS
// |------------------ used --| | used by your heap
// |-------init ---| | initialised amount of memory at the beginning (virtual memory can be not yet committed)
}
}
但是请记住,它等效于运行时
memoryMxBean.getHeapMemoryUsage().getUsed() <=> runtime.totalMemory() - runtime.freeMemory()
memoryMxBean.getHeapMemoryUsage().getCommitted() <=> runtime.totalMemory()
memoryMxBean.getHeapMemoryUsage().getMax() <=> runtime.maxMemory()
请参见here
作为附加说明,maxMemory小于-Xmx,因为至少必须有一个空的生存空间可用于堆分配。