系统会检测内存,如果内存占用过大,会自动清理,你查看一下系统日志/var/log/messages :
Sep 21 10:34:26 iZ94dvgpg40Z kernel: Out of memory: Kill process 11462 (java ) score 358 or sacrifice child
Sep 21 10:34:26 iZ94dvgpg40Z kernel: Killed process 11462 (java ) total-vm:3100672kB, anon-rss:695128kB, file-rss:0kB
参考
http://cn.v2ex.com/t/222457