linux限制用户内存使用

最近有内存使用报警的邮件发出，之后杀掉了内存占用高的进程，使内存恢复正常

但是发现某些程序被杀掉了，有过怀疑是被人手动杀掉的，看日志后发现应该是内存占用过大，系统自动杀掉的

内存耗尽会调用oom 对进程进行评估 并选择一个进程杀死 以释放内存

dmesg

Jun 26 08:45:47 localhost kernel: [6409835.925696] curl invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0
Jun 26 08:45:48 localhost kernel: [6409835.925705] curl cpuset=/ mems_allowed=0-1
Jun 26 08:45:48 localhost kernel: [6409835.925711] Pid: 3640, comm: curl Not tainted 3.2.0-41-generic #66-Ubuntu
Jun 26 08:45:48 localhost kernel: [6409835.925715] Call Trace:
Jun 26 08:45:48 localhost kernel: [6409835.925729]  [<ffffffff8111c281>] dump_header+0x91/0xe0
Jun 26 08:45:48 localhost kernel: [6409835.925734]  [<ffffffff8111c605>] oom_kill_process+0x85/0xb0
Jun 26 08:45:48 localhost kernel: [6409835.925740]  [<ffffffff8111c9aa>] out_of_memory+0xfa/0x220
...

Jun 26 08:45:48 localhost kernel: [6409836.005515] Out of memory: Kill process 13655 (sh) score 1 or sacrifice child
Jun 26 08:45:48 localhost kernel: [6409836.027998] Killed process 13657 (python) total-vm:1710324kB, anon-rss:2324kB, file-rss:360kB

系统限制用户内存使用量

cat /etc/security/limits.conf

ubuntu		soft	as	1200000
ubuntu		hard	as	1500000

系统内存情况

free

             total       used       free     shared    buffers     cached
Mem:       1015664     851624     164040        148     216548     378456
-/+ buffers/cache:     256620     759044
Swap:       999996       3344     996652

申请内存的代码

test.c

#include<stdio.h>
#include<stdlib.h>
size_t maximum=0;
int main(int argc,char *argv[])
{
    void * block;
    void * tmpblock;
    size_t blocksize[]={1024*1024, 1024, 1};
    int i,count;
    for(i=0;i<3;i++){
        for(count=1;;count++){
            block = malloc(maximum+blocksize[i]*count);
            if(block){
                tmpblock = block;
                maximum += blocksize[i]*count;
                free(block);
            }else{
                break;
            }
        }
    }
    printf("maximum malloc size = %lf GB\n",maximum*1.0 / 1024.0 / 1024.0 / 1024.0);
    printf("the address is %x\n",tmpblock);
    printf("the address end is %x\n", tmpblock + maximum);
    //while(1);
}

编译运行后的结果

gcc -o malloc  test.c
./malloc

maximum malloc size = 1.101562 GB
the address is 618c2010
the address end is a80c2010

去掉交换内存后的情况

free

             total       used       free     shared    buffers     cached
Mem:       1015664     856708     158956        384     216580     379532
-/+ buffers/cache:     260596     755068
Swap:            0          0          0

系统内存使用情况

./malloc

maximum malloc size = 0.784881 GB
the address is 3dc48010
the address end is 6fffff56

这个限制是包括交换内存在内的，系统会保留一定的内存供内核使用，用户空间能够申请的内存使用量达不到最大值

附注：

限制用户的内存和cpu使用还可以通过cgroup的方式进行， 这一点还不熟，希望以后可以有机会用到