oom-killer

最新推荐文章于 2025-07-18 11:37:35 发布

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本文深入探讨了Linux系统在内存资源紧张时如何触发oom-killer机制，详细解析了其工作原理、内核代码位置、以及如何通过配置/调整参数避免不必要的进程被kill。包括oom-killer如何选择并kill占用内存较高的进程，以及如何通过配置/调整进程的oom_adj和oom_score_adj来影响被kill的风险。

内存不够时系统会启动oom-killer
~ # xxx_test 192.168.1.29 192.168.1.71
rtl8168: eth0: link up
info [create_socket_srv:354]: listening on port : 6789
info [listen_func:304]: connection[4] : 192.168.1.71:43786
[process_cmd:365]: $taes #cd
ft2_test invoked oom-killer: gfp_mask=0x200da, order=0, oom_score_adj=0
CPU: 0 PID: 107 Comm: ft2_test Not tainted 3.10.27+ #401
Stack : 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 8efc9b98
…

Call Trace:[<800144f4>] 0x800144f4
[<800144f4>] 0x800144f4
[<80446c20>] 0x80446c20
[<80189f04>] 0x80189f04
[<80066744>] 0x80066744
[<80028420>] 0x80028420
[<800665e8>] 0x800665e8
[<80066568>] 0x80066568
[<80066ff0>] 0x80066ff0
[<8006a648>] 0x8006a648
[<8018ed24>] 0x8018ed24
[<8007ba94>] 0x8007ba94
[<8007e370>] 0x8007e370
[<8007e040>] 0x8007e040
[<800804a8>] 0x800804a8
[<8007bc88>] 0x8007bc88
[<80017428>] 0x80017428
[<800809c4>] 0x800809c4
[<8018add4>] 0x8018add4
[<80073cdc>] 0x80073cdc
[<8007f76c>] 0x8007f76c
[<8018add4>] 0x8018add4
[<8007eeac>] 0x8007eeac
[<80011ba4>] 0x80011ba4
[<8018eb98>] 0x8018eb98

Mem-Info:
Normal per-cpu:
CPU 0: hi: 90, btch: 15 usd: 33
active_anon:42496 inactive_anon:0 isolated_anon:0
active_file:0 inactive_file:2 isolated_file:0
unevictable:958 dirty:0 writeback:0 unstable:0
free:427 slab_reclaimable:163 slab_unreclaimable:343
mapped:156 shmem:0 pagetables:54 bounce:0
free_cma:0
Normal free:1708kB min:1728kB low:2160kB high:2592kB active_anon:169984kB inactive_anon:0kB active_file:0kB inactive_file:8kB unevictable:3832kB isolated(anon):0kB isolated(file):0kB present:262144kB managed:187256kB mlocked:0kB dirty:0kB writeback:0kB mapped:624kB shmem:0kB slab_reclaimable:652kB slab_unreclaimable:1372kB kernel_stack:272kB pagetables:216kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:46 all_unreclaimable? yes
lowmem_reserve[]: 0 0
Normal: 1*4kB (M) 1*8kB (U) 2*16kB (UM) 0*32kB 2*64kB (UM) 0*128kB 0*256kB 1*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 1708kB
960 total pagecache pages
65536 pages RAM
18347 pages reserved
270083 pages shared
44021 pages non-shared
[ pid ] uid tgid total_vm rss nr_ptes swapents oom_score_adj name
[ 84] 0 84 214 96 3 0 0 sh
[ 96] 0 96 46273 42577 48 0 0 ft2_test
Out of memory: Kill process 96 (ft2_test) score 873 or sacrifice child
Killed process 96 (ft2_test) total-vm:185092kB, anon-rss:169872kB, file-rss:436kB
Killed

oom-killer
oom-killer相关的内核代码位置在mm/oom-kill.c
oom-killer会在内存紧张的时候，依次kill内存占用较高的进程，发送signal 15(SIGTERM)，并在/var/log/message中进行记录。

Oom-kill杀死进程的机制
/proc/vm/oom_adj 表示该pid进程被oom killer杀掉的权重，在[-17, 15]之间，越高的权重，意味着越有可能被oom-killer选中，-17表示禁止被kill掉。
/proc/vm/oom_score 当前进程被kill的分数，越高的分数，意味着越有可能被kill