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,它目前正在使用17GB的OS内存.
我意识到JVM可以使用超过最大堆的使用,但我们使用15GB以上看起来很疯狂.
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 ....
(注意它使用的是0.017TB或17GB).
我尝试使用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.
并且...
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,我知道与类加载器有奇怪的事情,但我认为-permstat应该考虑到这一点,所以我很难过.
有任何想法吗？
约翰
请注意，堆区域（由Xmx限制）只是JVM进程的一部分。
基本上，JVM占用的内存是以下各项的总和：
可能还有更多，您可以通过谷歌搜索找到它：)
因此，您必须检查所有这些区域，以确保正在消耗内存。
我敢打赌，您的线程泄漏很简单-数千个线程会吃掉很多内存（正如我所说，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> dumpfile.txt）以查看是否存在问题。
当然也可以是使用本机缓冲区或JNI的外部库，但是可能性较小。
所以我们发现了这一点，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，以防它对将来的任何人有帮助。
问题只是没有关闭使用 Class.getInputAsStream() 读取的资源上打开的流。
之所以会出现混乱，是因为 JVM 堆的使用量可以忽略不计，但每个未关闭的流不知何故留下了一些已分配但未释放的本机代码。
因为没有文件句柄泄漏（可能是因为我们每次都从主 JAR 文件中读取，所以它重复使用相同的句柄），并且因为 JVM 堆使用量很小，所以我们直到实际使用时才发现它。做了堆转储。
无论如何，这个故事的寓意是不要犯我所犯的错误，即假设如果 JVM 堆使用率较低，则没有必要查看堆转储，因为在这种情况下，看到仍然分配的数千个对象会导致我们一条线索。
谢谢大家！
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