It would not be difficult to modify Airplane's memory management routines so that the blocks of memory returned by ::operator new were automatically released when they were no longer in use, but there are two reasons why you might not want to do it. ¤ Item E10, P29
这段是说，如果你想修改前面写好的那些内存管理程序（也就是他说的POOL拉），使得它能够自动释放掉从系统申请的内存（by ::operator new），是不难地（之所以有这种需求，考虑一下如果忽然有5000架飞机，然后又很长一段时间内没有飞机，那么前面的那些程序（pool）会hold住那5000架飞机的内存，很浪费），但是你不应该这么做，因为：
The first concerns your likely motivation for tackling custom memory management. There are many reasons why you might do it, but the most common one is that you've determined (see Item M16) that the default operator new and operator delete use too much memory or are too slow (or both). That being the case, every additional byte and every additional statement you devote to tracking and releasing those big memory blocks comes straight off the bottom line: your software runs slower and uses more memory than it would if you adopted the pool strategy. For libraries and applications in which performance is at a premium and you can expect pool sizes to be reasonably bounded, the pool approach may well be best. ¤ Item E10, P30
你之所以自己写内存管理（这个pool），就是因为你觉得缺省的new和delete用了太多内存且慢，所以，（如果你在pool的程序里添加自动释放内存的话），你devote的每一个额外的字节和额外的语句也有同样的效果：你的程序会占用更多内存且更慢，比你不用pool
然后继续：如果你的程序很注重效率且你能预计到pool的size的话（这样就不会造成上面说的内存浪费），你可以用pool
jjhou是对的，我没看过他的翻译，不知道上下文，这句的确切意思应该就是这样：如果你把pool复杂话了的话，还不如直接用缺省的new和delete，但是在能预计到pool的size的情况下，pool就可以非常简单且高效
