> From: "Erik Price" <[EMAIL PROTECTED]> > Sent: Monday, February 03, 2003 2:16 PM > Subject: Re: more about custam tag life cycle
> Are you saying that in general, object pooling is deprecated? In other > words, it's always a bad idea, with the exception of DataSource type pools? As a design issue, Object Pooling is frowned upon with the modern garbage collectors because short lived objects are "cheap". One of the original goals of Object Pooling was to put less strain on the GC by not creating lots of short term objects. With modern collectors, this is much less of an issue. For example, modern collectors during a GC will copy active objects. So, your GC time is relative to the number of active objects, rather than total allocated objects. For example, if you have 1000 active objects, and the GC will be copying them, then by the time the GC happens, it's essentially irrelevant whether you have 100 inactive objects or 100000000 inactive objects, your GC time will be the same. Therefore, the modern GCs are, if anything, "punishing" you for keeping objects around, rather than punishing you for simply creating objects. So, that means that whereas before the expense of an object was its creation, release, and GC, now the only expense is its creation and release. Of course, object creation is not free so as a general guideline it's better to minimize object creation in general. However, using an Object Pool is not necessarily prudent for generic objects, as you will be "punished" for saving them. Now, for objects that are especially expensive in their creation and are also inherently reusable, then pooling makes sense (and DB connections fall well into this category). All that being said, it does not mean the pooling within, say, a JSP code generator is necessarily bad. It can make the code a wee bit easier to create, as you simply surround Tag use (in this case) with "getOrCreateTagFromPool" and "placeTagBackInPool". This puts the burden of tracking used Tags and what not upon the JSP runtime, rather than the compiler. This is not a big deal in this case because the Object Pool could have a short life span and probably won't survive a GC. Anyway, in summary, as a general rule Object Pools are more expensive than they are worth with modern GCs. However, with a better understanding of them, you may find scenarios where they are worth utilizing. Regards, Will Hartung ([EMAIL PROTECTED]) --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
