内存占用造成OOM

[zhaibin18]

启动前
total used free shared buffers
Mem: 126472 32892 93580 632 1120
-/+ buffers: 31772 94700
Swap: 0 0 0

启动后
total used free shared buffers
Mem: 126472 94776 31696 632 1120
-/+ buffers: 93656 32816
Swap: 0 0 0

运行一段时间以后就OOM了：
Tue Dec 29 03:17:08 2015 kern.err kernel: [1023872.230000] Out of memory: Kill process 5331 (cow) score 819 or sacrifice child
Tue Dec 29 03:17:08 2015 kern.err kernel: [1023872.230000] Killed process 5331 (cow) total-vm:894172kB, anon-rss:106416kB, file-rss:12kB
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