centos7：无法分配内存 (errno=12)教程

启动项目报错：OpenJDK 64-Bit Server VM warning: INFO: os::commit\_memory(0x00000000f5a9b000, 66166784, 0) failed; error='无法分配内存' (errno=12)

部分日志内容：

\#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (mmap) failed to map 262144 bytes for committing reserved memory.
# Possible reasons:
# The system is out of physical RAM or swap space
# In 32 bit mode, the process size limit was hit
# Possible solutions:
# Reduce memory load on the system
# Increase physical memory or swap space
# Check if swap backing store is full
# Use 64 bit Java on a 64 bit OS
# Decrease Java heap size (-Xmx/-Xms)
# Decrease number of Java threads
# Decrease Java thread stack sizes (-Xss)
# Set larger code cache with -XX:ReservedCodeCacheSize=
# This output file may be truncated or incomplete.
#
# Out of Memory Error (os\_linux.cpp:2627), pid=25179, tid=0x00007fc9dea02700
#
# JRE version: Java(TM) SE Runtime Environment (8.0\_112-b15) (build 1.8.0\_112-b15)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.112-b15 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
#

通过命令查看，发现可用的物理内存还剩很多

linux参数之max\_map\_count

“This file contains the maximum number of memory map areas a process may have. Memory map areas are used as a side-effect of calling malloc, directly by mmap and mprotect, and also when loading shared libraries.

While most applications need less than a thousand maps, certain programs, particularly malloc debuggers, may consume lots of them, e.g., up to one or two maps per allocation.

The default value is 65536.”

max\_map\_count文件包含限制一个进程可以拥有的VMA(虚拟内存区域)的数量。

虚拟内存区域是一个连续的虚拟地址空间区域。

在进程的生命周期中，每当程序尝试在内存中映射文件，链接到共享内存段，或者分配堆空间的时候，这些区域将被创建。

调优这个值将限制进程可拥有VMA的数量。限制一个进程拥有VMA的总数可能导致应用程序出错，因为当进程达到了VMA上线但又只能释放少量的内存给其他的内核进程使用时，操作系统会抛出内存不足的错误。

如果你的操作系统在NORMAL区域仅占用少量的内存，那么调低这个值可以帮助释放内存给内核用。

调整示例

如下调整为默认的4倍

此操作需要root权限

临时修改：

[root@localhost ~]# sysctl -w vm.max\_map\_count=262144

永久修改：
直接写到/etc/sysctl.conf中,然后执行sysctl -p

[root@localhost ~]# vim /etc/sysctl.conf

vm.max\_map\_count=262144

[root@localhost ~]# sysctl -p

查看修改结果

[root@localhost ~]# sysctl -a|grep vm.max\_map\_count

vm.max\_map\_count = 262144