我有一个奇怪的问题：每个星期天早上 6 点，我的 LAMP 服务器都会崩溃。
查看日志时，我发现当时大约有 500 个 apache2 进程（这是一台没有任何负载的测试服务器 - 尤其是在早上 6 点）
系统日志声明如下：
May 19 06:00:11 myserver kernel: [313742.304291] Out of memory: Kill process 912 (mysqld) score 31 or sacrifice child
May 19 06:00:11 myserver kernel: [313742.304311] Killed process 912 (mysqld) total-vm:816528kB, anon-rss:6240kB, file-rss:0kB
看起来服务器内存不足，因此终止了一些进程。
可能是什么问题呢？ 这可能和每周的 crontab 有关吗？
以下是系统日志中的其他几行内容：
May 19 06:00:11 myserver kernel: [313742.290517] oom_kill_process: 3 callbacks suppressed
May 19 06:00:11 myserver kernel: [313742.290526] apache2 invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0
May 19 06:00:11 myserver kernel: [313742.290534] apache2 cpuset=/ mems_allowed=0
May 19 06:00:11 myserver kernel: [313742.290541] Pid: 1884, comm: apache2 Not tainted 3.2.0-29-generic #46-Ubuntu
May 19 06:00:11 myserver kernel: [313742.290546] Call Trace:
May 19 06:00:11 myserver kernel: [313742.290561] [<ffffffff810bf9ad>] ? cpuset_print_task_mems_allowed+0x9d/0xb0
May 19 06:00:11 myserver kernel: [313742.290570] [<ffffffff8111a7e1>] dump_header+0x91/0xe0
May 19 06:00:11 myserver kernel: [313742.290577] [<ffffffff8111ab65>] oom_kill_process+0x85/0xb0
May 19 06:00:11 myserver kernel: [313742.290584] [<ffffffff8111af0a>] out_of_memory+0xfa/0x220
May 19 06:00:11 myserver kernel: [313742.290592] [<ffffffff8112098f>] __alloc_pages_nodemask+0x80f/0x820
May 19 06:00:11 myserver kernel: [313742.290603] [<ffffffff8115937a>] alloc_pages_vma+0x9a/0x150
May 19 06:00:11 myserver kernel: [313742.290611] [<ffffffff811399cc>] do_anonymous_page.isra.38+0x7c/0x2f0
May 19 06:00:11 myserver kernel: [313742.290618] [<ffffffff8113d3f1>] handle_pte_fault+0x1e1/0x200
May 19 06:00:11 myserver kernel: [313742.290625] [<ffffffff8113d7c8>] handle_mm_fault+0x1f8/0x350
May 19 06:00:11 myserver kernel: [313742.290634] [<ffffffff8165d3e0>] do_page_fault+0x150/0x520
May 19 06:00:11 myserver kernel: [313742.290642] [<ffffffff81177d1d>] ? vfs_read+0x10d/0x180
May 19 06:00:11 myserver kernel: [313742.290649] [<ffffffff8165a035>] page_fault+0x25/0x30
May 19 06:00:11 myserver kernel: [313742.290653] Mem-Info:
May 19 06:00:11 myserver kernel: [313742.290657] Node 0 DMA per-cpu:
May 19 06:00:11 myserver kernel: [313742.290663] CPU 0: hi: 0, btch: 1 usd: 0
May 19 06:00:11 myserver kernel: [313742.290666] Node 0 DMA32 per-cpu:
May 19 06:00:11 myserver kernel: [313742.290672] CPU 0: hi: 186, btch: 31 usd: 124
May 19 06:00:11 myserver kernel: [313742.290682] active_anon:73974 inactive_anon:73976 isolated_anon:0
May 19 06:00:11 myserver kernel: [313742.290684] active_file:305 inactive_file:3393 isolated_file:0
May 19 06:00:11 myserver kernel: [313742.290687] unevictable:0 dirty:11 writeback:4 unstable:0
May 19 06:00:11 myserver kernel: [313742.290689] free:12251 slab_reclaimable:2341 slab_unreclaimable:19263
May 19 06:00:11 myserver kernel: [313742.290692] mapped:1006 shmem:37 pagetables:59627 bounce:0
May 19 06:00:11 myserver kernel: [313742.290697] Node 0 DMA free:4652kB min:684kB low:852kB high:1024kB active_anon:4380kB inactive_anon:4380kB active_file:0kB inactive_file:36kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15656kB mlocked:0kB dirty:0kB writeback:8kB mapped:0kB shmem:0kB slab_reclaimable:200kB slab_unreclaimable:212kB kernel_stack:0kB pagetables:2024kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:12 all_unreclaimable? yes
May 19 06:00:11 myserver kernel: [313742.290720] lowmem_reserve[]: 0 991 991 991
May 19 06:00:11 myserver kernel: [313742.290728] Node 0 DMA32 free:44352kB min:44368kB low:55460kB high:66552kB active_anon:291516kB inactive_anon:291524kB active_file:1220kB inactive_file:13536kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1014992kB mlocked:0kB dirty:44kB writeback:8kB mapped:4024kB shmem:148kB slab_reclaimable:9164kB slab_unreclaimable:76840kB kernel_stack:5112kB pagetables:236484kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:5925 all_unreclaimable? yes
May 19 06:00:11 myserver kernel: [313742.290752] lowmem_reserve[]: 0 0 0 0
May 19 06:00:11 myserver kernel: [313742.290759] Node 0 DMA: 11*4kB 18*8kB 39*16kB 46*32kB 3*64kB 1*128kB 0*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 4652kB
May 19 06:00:11 myserver kernel: [313742.290778] Node 0 DMA32: 54*4kB 119*8kB 121*16kB 79*32kB 49*64kB 26*128kB 12*256kB 7*512kB 3*1024kB 1*2048kB 5*4096kB = 44352kB
May 19 06:00:11 myserver kernel: [313742.290797] 10895 total pagecache pages
May 19 06:00:11 myserver kernel: [313742.290801] 7149 pages in swap cache
May 19 06:00:11 myserver kernel: [313742.290805] Swap cache stats: add 1460822, delete 1453673, find 653694/726620
May 19 06:00:11 myserver kernel: [313742.290809] Free swap = 0kB
May 19 06:00:11 myserver kernel: [313742.290812] Total swap = 2097084kB
May 19 06:00:11 myserver kernel: [313742.299856] 261856 pages RAM
May 19 06:00:11 myserver kernel: [313742.299860] 7335 pages reserved
May 19 06:00:11 myserver kernel: [313742.299863] 291314 pages shared
May 19 06:00:11 myserver kernel: [313742.299866] 239474 pages non-shared
答案1
问题似乎是由 Apache 服务器调优不当引起的。您不应该让 Apache 资源的增长速度超过内存或 CPU 的速度。
这个参考资料确实很有趣，值得一看：http://drupal.org/node/215516
答案2
我的一个 vSserver 有完全相同的问题。
很难确定因内存不足而导致崩溃的具体原因，但时间指向了 crontab.weekly。
在研究了crontab.weekly从不同的服务器中，我发现问题服务器比正常工作的服务器多了一个脚本：
apt-xapian-index
似乎“Debian 软件包 Xapian 索引维护工具”在使用的小型服务器和计算机上引发了很多问题。经过一番谷歌搜索后，我决定从 crontab.weekly 中删除该脚本，现在问题似乎已经消失。
我建议您尝试从 crontab.weekly 中删除该脚本和任何其他重量级脚本，看看是否有助于解决您的问题：)
答案3
问题在于 Apache 的设置MinSpareServers = 500导致单核测试服务器上的服务器负载始终 >>10。