我们遇到的问题是JVM比max -Xmx使用的要多得多。
我们正在使用-Xmx2048，目前它正在使用17GB的操作系统内存。
我意识到JVM可以使用超过最大堆的数量，但是我们使用的更多15GB似乎很疯狂。
顶部转储如下所示：
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
30477 root 20 0 22.683g 0.017t 18536 S 0.7 29.1 27:43.44 java -Xmx2048M -Xms1024M -XX:MaxPermSize=256M -XX:ReservedCodeCacheSize=128M ....
（注意它使用0.017TB或17GB）。
我尝试过使用jmap进行调试：
sudo jmap -J-d64 -heap 30477
Attaching to process ID 30477, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04
using thread-local object allocation.
Parallel GC with 8 thread(s)
Heap Configuration:
MinHeapFreeRatio = 0
MaxHeapFreeRatio = 100
MaxHeapSize = 2147483648 (2048.0MB)
NewSize = 1310720 (1.25MB)
MaxNewSize = 17592186044415 MB
OldSize = 5439488 (5.1875MB)
NewRatio = 2
SurvivorRatio = 8
PermSize = 21757952 (20.75MB)
MaxPermSize = 268435456 (256.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 316145664 (301.5MB)
used = 150828136 (143.8409194946289MB)
free = 165317528 (157.6590805053711MB)
47.708431009827166% used
From Space:
capacity = 20447232 (19.5MB)
used = 3406624 (3.248809814453125MB)
free = 17040608 (16.251190185546875MB)
16.660563151041668% used
To Space:
capacity = 21495808 (20.5MB)
used = 0 (0.0MB)
free = 21495808 (20.5MB)
0.0% used
PS Old Generation
capacity = 716177408 (683.0MB)
used = 516302952 (492.3848648071289MB)
free = 199874456 (190.6151351928711MB)
72.09148825873044% used
PS Perm Generation
capacity = 56098816 (53.5MB)
used = 55842840 (53.255882263183594MB)
free = 255976 (0.24411773681640625MB)
99.54370516482915% used
15065 interned Strings occupying 1516808 bytes.
还有......
sudo jmap -J-d64 -permstat 30477
Attaching to process ID 30477, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04
finding class loader instances ..done.
computing per loader stat ..done.
please wait.. computing liveness...liveness analysis may be inaccurate ...
class_loader classes bytes parent_loader alive? type
<bootstrap> 1908 11793728 null live <internal>
0x0000000780b97590 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b99b28 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b96cb0 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113ca0 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b97c90 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114458 1 3048 null dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b892b0 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b989a8 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780019cf0 7731 44085000 0x0000000780019d40 live sun/misc/Launcher$AppClassLoader@0x0000000770239a20
0x0000000780113f10 1 3152 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780aa8918 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114008 1 3040 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b7a8b8 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780d236d0 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780019d40 207 1327296 null live sun/misc/Launcher$ExtClassLoader@0x00000007701eb8b8
0x0000000780113e28 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x00000007801140b0 1 3064 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x000000078dc814f8 1 3024 null dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b8abf8 1 3208 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b990a8 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114130 1 1904 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b98010 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x00000007801141b0 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113620 27 86320 0x0000000780019cf0 live org/apache/tapestry5/internal/plastic/PlasticClassLoader@0x000000077181b058
0x0000000780114418 1 3064 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b98d28 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b89270 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113ed0 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b97910 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b997a8 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b96930 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780d36d38 1 3024 0x0000000780019d40 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b99ea8 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780bddff8 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780a63ca0 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114048 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113fc8 1 3024 null dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113de8 1 3072 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b7afb8 1 3040 null dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113e68 1 1904 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b7ac38 1 1880 null dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780113d58 1 3064 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x00000007801140f0 1 3280 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b98628 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x000000078088f900 0 0 0x0000000780019cf0 dead java/util/ResourceBundle$RBClassLoader@0x00000007709cda40
0x0000000780b99428 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780d28ba0 1 3024 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b97030 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114170 1 3064 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x00000007801143d8 1 3048 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780114240 1 1880 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
0x0000000780b8af60 1 3104 0x0000000780019cf0 dead sun/reflect/DelegatingClassLoader@0x0000000770059770
total = 53 9921 57418080 N/A alive=4, dead=49 N/A
该应用程序是一个Play应用程序，我知道这对类加载器来说很奇怪，但我认为-permstat应该考虑到这一点，所以我很难过。
有什么想法吗？
约翰
答案 0 :(得分：4)
请注意，堆区域（以Xmx为界）只是JVM进程的一部分。
基本上JVM占用的内存是：
的总和可能还有更多，你可以通过谷歌搜索找到它：）
所以你必须检查所有这些区域，以确保消耗内存。
我敢打赌你有简单的线程泄漏 - 成千上万的线程会占用大量内存（正如我所说的，假设每个线程1MB，10000个线程对应10GB内存）。您可以简单地进行线程转储（jstack -l＆gt; dumpfile.txt）以查看它是否存在问题。
当然它也可能是使用本机缓冲区或JNI的外部库，但它的可能性较小。
答案 1 :(得分：2)
所以我们想出来了，这只是开发人员的错误。感谢所有建议的帮助。
无论如何我都会回答这个问题，以防将来有人帮忙。
问题只是没有关闭使用Class.getInputAsStream（）读取资源的流。
由于JVM堆使用量可以忽略不计，因此产生了混淆，但是每个未关闭的流以某种方式分配了一些本机代码并且未被释放。
因为没有文件句柄泄漏（大概是因为我们每次都从主JAR文件中读取它，它重新使用相同的句柄），并且因为JVM堆使用很少，所以我们没有＆＃39 ; t发现它直到我们实际进行堆转储。
无论如何，故事的寓意是不要犯下我所犯的错误，这假设如果JVM堆使用率很低，那么看堆堆转储是没有意义的，因为在这种情况下看到数千仍然分配的对象给了我们一个线索。
全部谢谢！