JRE 不足 memory 问题即使有足够的 memory？

Question

我在 linux 操作系统服务器上运行 JAVA 程序并尝试将一些信息推送到 RabbitMQ。 由于Out of Memory 错误，程序以某种方式被中断。 我正在尝试更多调查并找出原因，但是日志文件中的内容非常丰富，我想寻求一些帮助，因为我也是Java的新手。

我不指望我直接在这里得到答案（但如果可以的话我会很高兴），只是想得到正确的方向，以免浪费太多时间。 任何帮助将不胜感激！ 提前致谢！

以下是一些有价值的信息

# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (mmap) failed to map 55574528 bytes for committing reserved memory.

#  Out of Memory Error (os_linux.cpp:2795), pid=43653, tid=0x00007f46186b4700
#
# JRE version: OpenJDK Runtime Environment (8.0_332-b09) (build 1.8.0_332-b09)
# Java VM: OpenJDK 64-Bit Server VM (25.332-b09 mixed mode linux-amd64 compressed oops)
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#

---------------  T H R E A D  ---------------

Current thread (0x00007f46280ea000):  VMThread [stack: 0x00007f46185b5000,0x00007f46186b5000] [id=43657]

Stack: [0x00007f46185b5000,0x00007f46186b5000],  sp=0x00007f46186b3330,  free space=1016k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0xb65ecd]  VMError::report_and_die()+0x1cd
V  [libjvm.so+0x5075aa]  report_vm_out_of_memory(char const*, int, unsigned long, VMErrorType, char const*)+0xaa
V  [libjvm.so+0x941588]  os::pd_commit_memory(char*, unsigned long, unsigned long, bool)+0xd8
V  [libjvm.so+0x938d9e]  os::commit_memory(char*, unsigned long, unsigned long, bool)+0x2e
V  [libjvm.so+0x9b902b]  PSVirtualSpace::expand_by(unsigned long)+0x5b
V  [libjvm.so+0x9a90ca]  PSOldGen::expand_by(unsigned long) [clone .part.113]+0x2a
V  [libjvm.so+0x9a929b]  PSOldGen::expand(unsigned long) [clone .part.115]+0xdb
V  [libjvm.so+0x9a9be8]  PSOldGen::resize(unsigned long)+0x198
V  [libjvm.so+0x9af58c]  PSParallelCompact::invoke_no_policy(bool)+0x9dc
V  [libjvm.so+0x9b6b7d]  PSScavenge::invoke()+0x17d
V  [libjvm.so+0x968c73]  ParallelScavengeHeap::failed_mem_allocate(unsigned long)+0x63
V  [libjvm.so+0xb67b23]  VM_ParallelGCFailedAllocation::doit()+0x93
V  [libjvm.so+0xb6cfe5]  VM_Operation::evaluate()+0x55
V  [libjvm.so+0xb6afaa]  VMThread::evaluate_operation(VM_Operation*)+0x11a
V  [libjvm.so+0xb6b419]  VMThread::loop()+0x219
V  [libjvm.so+0xb6b8d2]  VMThread::run()+0x92
V  [libjvm.so+0x93e4f2]  java_start(Thread*)+0xf2

VM_Operation (0x00007f463172d3e0): ParallelGCFailedAllocation, mode: safepoint, requested by thread 0x00007f4628063800

我在这里看到的是我有足够的免费 memory 来分配（MemFree），对吧？

---------------  S Y S T E M  ---------------

OS:CentOS Linux release 7.8.2003 (Core)

uname:Linux 3.10.0-1160.62.1.el7.x86_64 #1 SMP Tue Apr 5 16:57:59 UTC 2022 x86_64
libc:glibc 2.17 NPTL 2.17 
rlimit: STACK 8192k, CORE 0k, NPROC 4096, NOFILE 4096, AS infinity
load average:4.81 6.40 3.68

/proc/meminfo:
MemTotal:        3861256 kB
MemFree:          108460 kB
MemAvailable:      19104 kB
Buffers:               0 kB
Cached:            22388 kB
SwapCached:         7600 kB
Active:          2577112 kB
Inactive:         971876 kB
Active(anon):    2570780 kB
Inactive(anon):   957160 kB
Active(file):       6332 kB
Inactive(file):    14716 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       1048572 kB
SwapFree:            780 kB
Dirty:                20 kB
Writeback:             0 kB
AnonPages:       3519584 kB
Mapped:             3356 kB
Shmem:              1184 kB
Slab:              85128 kB
SReclaimable:      40496 kB
SUnreclaim:        44632 kB
KernelStack:        7872 kB
PageTables:        20908 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     2979200 kB
Committed_AS:    3444760 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      183428 kB
VmallocChunk:   34359310332 kB
Percpu:            24064 kB
HardwareCorrupted:     0 kB
AnonHugePages:    448512 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       94016 kB
DirectMap2M:     4100096 kB
DirectMap1G:     2097152 kB

Answer 1

我在这里看到的是我有足够的免费 memory 来分配（MemFree），对吧？

不，应用程序不能使用所有物理 memory； Linux 保留一定数量的空闲 RAM 专供 kernel 使用。 这可以通过vm.min_free_kbytes sysctl 选项进行配置，默认值通常为 44-66 MB。

$ sudo sysctl vm.min_free_kbytes
vm.min_free_kbytes = 45056

即使有足够的空闲 RAM，分配也可能由于其他限制而失败，例如

• vm.max_map_count
• vm.overcommit_memory , vm.overcommit_ratio
• RLIMIT_AS

有关详细信息，请参阅此答案。