overcommit_memory

/etc/sysctl.conf                                                                                                                                                                                                                                          
vm.overcommit_memory=1   
或者
sysctl vm.overcommit_memory=1   
或者   

echo 1 > /proc/sys/vm/overcommit_memory                                                                                                                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                                                                                                                                                           
内核参数说明如下：                                                                                                                                                                                                     
overcommit_memory文件指定了内核针对内存分配的策略，其值可以是0、1、2

• 0， 表示内核将检查是否有足够的可用内存供应用进程使用；如果有足够的可用内存，内存申请允许；否则，内存申请失败，并把错误返回给应用进程
• 1， 表示内核允许分配所有的物理内存，而不管当前的内存状态如何
• 2， 表示内核允许分配超过所有物理内存和交换空间总和的内存

                             

http://blog.csdn.net/anghlq/article/details/7087069