我正在阅读以下文章：http://java.sun.com/docs/hotspot/gc1.4.2/example.html，无法理解以下几行：
Young generation size is too small
The young generation heap size in this first example is about 4 Mbytes with an overall heap size of about 32 Mbytes.
[GC [DefNew: 4032K->64K(4032K), 0.0429742 secs] 9350K->7748K(32704K), 0.0431096 secs]
[GC [DefNew: 4032K->64K(4032K), 0.0403446 secs] 11716K->10121K(32704K), 0.0404867 secs]
[GC [DefNew: 4032K->64K(4032K), 0.0443969 secs] 14089K->12562K(32704K), 0.0445251 secs]
This output seems reasonable from the point of view of the time spent in garbage collection but note that although the occupancy of the young generation is decreasing (e.g., in the first line from 4032 to 64k by 3968k) the occupancy of the entire heap is decreasing by considerably less (by 1602k from 9350k to 7748k). This indicates that only about 40% objects in the young generation were garbage and the rest survive the collection and are being promoted into the old generation.
Increasing the young generation size to increase the free space after the collection
The young generation heap size in this next run is increased to 8 Mbytes.
[GC [DefNew: 8128K->64K(8128K), 0.0453670 secs] 13000K->7427K(32704K), 0.0454906 secs]
[GC [DefNew: 8128K->64K(8128K), 0.0388632 secs] 15491K->9663K(32704K), 0.0390013 secs]
[GC [DefNew: 8128K->64K(8128K), 0.0388610 secs] 17727K->11829K(32704K), 0.0389919 secs]
With an 8 Mbyte size most of young generation is garbage at the time of the minor collection. In the first line the young generation heap decreases by 8064k from 8128k to 64k and the entire heap decreases by 5573k from 13000k to 7427k meaning about 68% of the young generation was garbage. As would be expected the size of the young generation does not change the amount of live objects that survive the minor collection (about 2.4M bytes in each case) but there are fewer minor collections and the cost of the collections in terms of the minor collection pause times are comparable (fractions of a second listed at the end of each line).
我的问题是，在这种情况下，增加YoungGen的大小将如何帮助我们。应用程序在YoungGen中分配的对象总数将保持不变。
最佳答案
答案在于文章本身。
不出所料，年轻一代的规模不会改变
在次要收藏中存活的活物数量（约
每种情况下为240万字节），但次要集合的数量较少，而次要集合的暂停时间则减少了集合的成本
是可比较的（每行末尾列出了几分之一秒）。
这是增加YoungGen的直接结果。