【发布时间】：2013-09-08 23:03:57
【问题描述】：
我正在测试 Web 应用程序的性能，并且出现“内存不足错误”（本机内存）。
我测试了好几次，每次都“为 Chunk::new 分配 83886088 字节失败”而死。
我每分钟打印一次内存大小，发现进程死亡前的VmSize是2924700 kB。
我认为已达到进程大小限制。我把 -Xmx2000m 改成 -Xmx1900m 就可以了。
一些问题：
1.如何确认已达到进程大小限制。不完全是 3G 内存。
2.为什么JVM每次都分配83886088字节的内存？从异常栈看，似乎和GC的事情有关。
3.JVM除了堆内存（-Xmx）和非堆内存（-XX:MaxPermSize）外，还应该保留多少内存？以及如何知道它现在使用了多少？
感谢并为我糟糕的英语感到抱歉。
Linux 2.6.16.60-0.83.2-bigsmp JRE 6.0_25-b06 雄猫 7.0.37
jvm options: -Xms2000m -Xmx2000m -XX:PermSize=256M -XX:MaxPermSize=512m -XX:+UseConcMarkSweepGC -XX:+UseParNewGC
/proc/meminfo:
MemTotal: 24935548 kB
MemFree: 13564968 kB
# Native memory allocation (malloc) failed to allocate 83886088 bytes for Chunk::new
# Possible reasons:
# The system is out of physical RAM or swap space
# In 32 bit mode, the process size limit was hit
...
# This output file may be truncated or incomplete.
#
# Out of Memory Error (allocation.cpp:317), pid=18217, tid=275671968
--------------- T H R E A D ---------------
Current thread (0x105a1c00): VMThread [stack: 0x10666000,0x106e7000] [id=18243]
Stack: [0x10666000,0x106e7000], sp=0x106e5ae0, free space=510k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x724710] VMError::report_and_die()+0x2b0
V [libjvm.so+0x2f68ef] report_vm_out_of_memory(char const*, int, unsigned, char const*)+0x4f
V [libjvm.so+0x1576fc] Chunk::operator new(unsigned, unsigned)+0x5c
V [libjvm.so+0x157c26] Arena::grow(unsigned)+0x26
V [libjvm.so+0x6457e9] resource_allocate_bytes(unsigned)+0x49
V [libjvm.so+0x3a03ef] GenericGrowableArray::raw_allocate(int)+0xbf
V [libjvm.so+0x3402ee] GrowableArray<oopDesc*>::grow(int)+0x3e
V [libjvm.so+0x3a62b1] FindInstanceClosure::do_object(oopDesc*)+0x51
V [libjvm.so+0x2ae571] CompactibleFreeListSpace::object_iterate(ObjectClosure*)+0x51
V [libjvm.so+0x38d066] GenerationObjIterateClosure::do_space(Space*)+0x16
V [libjvm.so+0x2d6498] ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure*, bool)+0x18
V [libjvm.so+0x38be22] Generation::object_iterate(ObjectClosure*)+0x22
V [libjvm.so+0x2d9f9d] ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure*)+0x4d
V [libjvm.so+0x37fd65] GenCollectedHeap::object_iterate(ObjectClosure*)+0x55
V [libjvm.so+0x3a61fe] HeapInspection::find_instances_at_safepoint(klassOopDesc*, GrowableArray<oopDesc*>*)+0x3e
V [libjvm.so+0x6eca91] ConcurrentLocksDump::dump_at_safepoint()+0xf1
V [libjvm.so+0x6e7561] Threads::print_on(outputStream*, bool, bool, bool)+0x201
V [libjvm.so+0x734927] VM_PrintThreads::doit()+0x27
V [libjvm.so+0x734576] VM_Operation::evaluate()+0x46
V [libjvm.so+0x733a23] VMThread::evaluate_operation(VM_Operation*)+0x83
V [libjvm.so+0x733c90] VMThread::loop()+0x190
V [libjvm.so+0x733780] VMThread::run()+0x80
V [libjvm.so+0x5e294e] java_start(Thread*)+0x14e
C [libpthread.so.0+0x54ab] short+0x8b
VM_Operation (0x0caff000): PrintThreads, mode: safepoint, requested by thread 0x09ec3800
--------------- P R O C E S S ---------------
Java Threads: ( => current thread )
...//209 Java Threads
Heap
par new generation total 147456K, used 126550K [0x161f0000, 0x201f0000, 0x201f0000)
eden space 131072K, 92% used [0x161f0000, 0x1d869d18, 0x1e1f0000)
from space 16384K, 31% used [0x1e1f0000, 0x1e70be78, 0x1f1f0000)
to space 16384K, 0% used [0x1f1f0000, 0x1f1f0000, 0x201f0000)
concurrent mark-sweep generation total 1884160K, used 1697819K [0x201f0000, 0x931f0000, 0x931f0000)
concurrent-mark-sweep perm gen total 262144K, used 61769K [0x931f0000, 0xa31f0000, 0xb31f0000)
Code Cache [0xb391f000, 0xb44b7000, 0xb691f000)
total_blobs=3924 nmethods=3719 adapters=157 free_code_cache=38272704 largest_free_block=9600
【问题讨论】：
-
你为什么要使用 32 位？如果你不能使用 64 位，我至少会使用 Java 6 update 45 而不是 update 25。
-
还有其他程序，替换它们需要花费很多时间。