Java内存不足错误（本机内存），达到进程大小限制（32位linux）

我正在测试 Web 应用程序的性能，并收到“内存不足错误”（本机内存）。

我测试了好几次，每次都是“无法为 Chunk::new 分配 83886088 字节”并死掉。

我每分钟打印一次内存大小，发现进程死亡前VmSize为2924700 kB。

我认为已达到进程大小限制。我将 -Xmx2000m 更改为 -Xmx1900m 现在就可以了。

一些问题：

1.如何确认是否达到进程大小限制。不完全是3G内存。

2.为什么JVM每次分配83886088字节内存？从异常堆栈来看，好像和GC的事情有关。

3.除了堆内存(-Xmx)和非堆内存(-XX:MaxPermSize)之外，还应该为JVM保留多少内存？如何知道现在使用了多少？

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

每分钟打印一次内存大小，发现进程死亡前VmSize为2924700 kB。

AFAIK 在 Linux 上，操作系统使用大约 1 GB。您需要用于线程堆栈、共享库、永久代、内存映射文件和任何本机资源的虚拟内存。

如果您接近此限制（或者如果您只有 64 位处理器），您确实应该使用 64 位操作系统和 JVM。如果不是 Java 7 更新 25，我会使用 Java 6 更新 45，这是免费支持的结束。