linux - 带有大量 RAM 的 Oom-killer(内存不足)(？!)- inotify

Question

我面临着将 inotify 放入大量文件夹(~2 000 000)的问题。我将 max_user_watches 更改为 8388608 :

echo 8388608 > /proc/sys/fs/inotify/max_user_watches

为了支持这个数量的 watch ，服务器有 3Gb 的可用内存。但是当我启动 inotify 脚本时，几个小时后(~15 小时)，它被杀死了。这是/var/log/messages 跟踪:

inotify.sh invoked oom-killer: gfp_mask=0xd0, order=1, oom_adj=0
inotify.sh cpuset=/ mems_allowed=0
Pid: 12488, comm: inotify.sh Not tainted 2.6.32-5-686 #1
Call Trace:
 [<c1089534>] ? oom_kill_process+0x60/0x201
 [<c1089ab1>] ? __out_of_memory+0xf4/0x107
 [<c1089b1e>] ? out_of_memory+0x5a/0x7c
 [<c108c3c9>] ? __alloc_pages_nodemask+0x3ef/0x4d9
 [<c108c4bf>] ? __get_free_pages+0xc/0x17
 [<c102f06c>] ? copy_process+0xb7/0xf28
 [<c11028ad>] ? security_file_alloc+0xc/0xd
 [<c1030017>] ? do_fork+0x13a/0x2bc
 [<c10b182d>] ? fd_install+0x1e/0x3c
 [<c103b996>] ? recalc_sigpending+0xf/0x2e
 [<c103bcae>] ? sigprocmask+0x9d/0xbc
 [<c1001dae>] ? sys_clone+0x21/0x27
 [<c10030fb>] ? sysenter_do_call+0x12/0x28
Mem-Info:
DMA per-cpu:
CPU    0: hi:    0, btch:   1 usd:   0
CPU    1: hi:    0, btch:   1 usd:   0
Normal per-cpu:
CPU    0: hi:  186, btch:  31 usd:   0
CPU    1: hi:  186, btch:  31 usd:  41
HighMem per-cpu:
CPU    0: hi:  186, btch:  31 usd:   0
CPU    1: hi:  186, btch:  31 usd:  34
active_anon:53061 inactive_anon:13287 isolated_anon:0
 active_file:2006 inactive_file:4143 isolated_file:0
 unevictable:0 dirty:272 writeback:0 unstable:0
 free:499244 slab_reclaimable:174921 slab_unreclaimable:25041
 mapped:1892 shmem:42 pagetables:240 bounce:0
DMA free:3492kB min:64kB low:80kB high:96kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15804kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:12080kB slab_unreclaimable:332kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
lowmem_reserve[]: 0 861 3032 3032
Normal free:59488kB min:3720kB low:4648kB high:5580kB active_anon:0kB inactive_anon:0kB active_file:1092kB inactive_file:3380kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:881880kB mlocked:0kB dirty:1088kB writeback:0kB mapped:4kB shmem:0kB slab_reclaimable:687604kB slab_unreclaimable:99832kB kernel_stack:952kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:1211 all_unreclaimable? yes
lowmem_reserve[]: 0 0 17366 17366
HighMem free:1933996kB min:512kB low:2856kB high:5200kB active_anon:212244kB inactive_anon:53148kB active_file:6932kB inactive_file:13192kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2222948kB mlocked:0kB dirty:0kB writeback:0kB mapped:7564kB shmem:168kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:960kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
DMA: 19*4kB 43*8kB 16*16kB 6*32kB 17*64kB 12*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3492kB
Normal: 14406*4kB 99*8kB 1*16kB 3*32kB 1*64kB 1*128kB 1*256kB 1*512kB 0*1024kB 0*2048kB 0*4096kB = 59488kB
HighMem: 31*4kB 14*8kB 8*16kB 2*32kB 2*64kB 1*128kB 2*256kB 1*512kB 1*1024kB 1*2048kB 471*4096kB = 1933996kB
6194 total pagecache pages
0 pages in swap cache
Swap cache stats: add 0, delete 0, find 0/0
Free swap  = 1951736kB
Total swap = 1951736kB
786416 pages RAM
560130 pages HighMem
7712 pages reserved
7694 pages shared
275891 pages non-shared

当脚本被终止时，我有将近 2Gb 的空闲内存。所以我不是很理解这个OOM。有人能帮我吗 ？该脚本非常简单:

#!/bin/bash

INOTIFY_DIR="/data"
inotifywait -rme modify,attrib,move,close_write,create,delete,delete_self $INOTIFY_DIR 2>> /datatest/inotify.log

Answer 1

OOM killer 与 page_fault_handler() 相关联。如果 page_fault_handler 由于不可用而无法分配页面，它将通过内核调用 page_fault_out_of_memory() 调用 OOM killer。然后 OOM killer 逻辑将启动并选择最佳候选进程来杀死和清理内存。该逻辑遵循一种启发式方法来找到最可杀死的进程，以便它可以释放内存并保持系统事件。

为什么 OOM killer 会启动完全基于空闲页面的可用性。这可能是来自任何内存区域的页面分配失败。您有足够大的可用内存并不意味着您在所有其他区域中都有可用内存。等 ZONE_DMA，低内存等

查看 oom_kill.c 中的 page_fault_out_of_memory() 了解有关 oom killer 算法的更多详细信息