明明什么都没干，想问一下为什么会used 2480K呢？

环境
ubuntu14.10 + jdk8

运行程序

java
public class Test {
    public static void main(String[] args) {
    }
}
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jvm参数

java
-verbose:gc -Xms20M -Xmx20m -Xmn10M -XX:SurvivorRatio=8  -XX:+PrintGCDetails
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GC日志

java
Heap
 PSYoungGen      total 9216K, used 2480K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)
  eden space 8192K, 30% used [0x00000000ff600000,0x00000000ff86c050,0x00000000ffe00000)
  from space 1024K, 0% used [0x00000000fff00000,0x00000000fff00000,0x0000000100000000)
  to   space 1024K, 0% used [0x00000000ffe00000,0x00000000ffe00000,0x00000000fff00000)
 ParOldGen       total 10240K, used 0K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)
  object space 10240K, 0% used [0x00000000fec00000,0x00000000fec00000,0x00000000ff600000)
 Metaspace       used 3522K, capacity 4588K, committed 4864K, reserved 1056768K
  class space    used 386K, capacity 433K, committed 512K, reserved 1048576K
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