最近有內存使用報警的郵件發出，之后殺掉了內存占用高的進程，使內存恢復正常
但是發現某些程序被殺掉了，有過懷疑是被人手動殺掉的，看日志后發現應該是內存占用過大，系統自動殺掉的
內存耗盡會調用oom 對進程進行評估 並選擇一個進程殺死 以釋放內存
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
系統限制用戶內存使用量
cat /etc/security/limits.conf
ubuntu soft as 1200000
ubuntu hard as 1500000
系統內存情況
free
total used free shared buffers cached
Mem: 1015664 851624 164040 148 216548 378456
-/+ buffers/cache: 256620 759044
Swap: 999996 3344 996652
申請內存的代碼
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);
}
編譯運行后的結果
gcc -o malloc test.c
./malloc
maximum malloc size = 1.101562 GB
the address is 618c2010
the address end is a80c2010
去掉交換內存后的情況
free
total used free shared buffers cached
Mem: 1015664 856708 158956 384 216580 379532
-/+ buffers/cache: 260596 755068
Swap: 0 0 0
系統內存使用情況
./malloc
maximum malloc size = 0.784881 GB
the address is 3dc48010
the address end is 6fffff56
這個限制是包括交換內存在內的，系統會保留一定的內存供內核使用，用戶空間能夠申請的內存使用量達不到最大值
附注：
限制用戶的內存和cpu使用還可以通過cgroup的方式進行， 這一點還不熟，希望以后可以有機會用到