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
",maximum*1.0 / 1024.0 / 1024.0 / 1024.0);
printf("the address is %x
",tmpblock);
printf("the address end is %x
", 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