On Jun 10, 2010, at 1:42 AM, Adrian Crum wrote: > I backed it up in an indirect way by mentioning the need to understand the > Javolution library and its intended use. Go here to find out more: > > http://javolution.org/ > > To summarize: Javolution was intended to be used in real-time systems where > timing is critical. The library's goal is timing that is *consistent*, not > necessarily fast. > > OFBiz is not a real-time application - it isn't being used to control robots > or Mars rovers or anything timing-critical like that.
That's hardly the only goal for Javolution, and certainly not the reason it is used in OFBiz. The main reasons were object pooling/reuse and faster Map (and sometimes List) performance for those that are pretty dynamic during their life (even if it is short). > You have to spend time on the Javolution site and poke around in their code a > bit to understand the advantages/disadvantages. Adam has mentioned some of > them in this thread and in previous threads. > > FastList implements a doubly-linked list. The list nodes are kept in an > object pool. ArrayList wraps an array. If you think about it, the > advantages/disadvantages will start to become evident. FastList will perform > additions and removals more consistently than ArrayList because the change > involves adding/removing a node. ArrayList resizes/copies the array it wraps, > so the timing depends on the size of the array. A doubly-linked list will > take more memory than ArrayList because the list elements are wrapped with > nodes. An ArrayList will take more memory than the array it wraps because it > contains additional bookkeeping data. There's really quite a bit more to it than that, ie lots of reasons to choose a linked list, doubly linked list, or an array (in Java either literal or array list). However, for most of OFBiz chances are it won't make much of a difference in memory usage or execution time. The fact is these things do get complicated and it's nice to know about different options and what might work better in a certain circumstance, but just because in theory it might use less memory or execute faster doesn't mean that it actually will, or it might make a difference but not a measurable one by even a performance testing tool and certainly not something that even on a larger scale a user would notice because other factors dominate so much that such changes are little more than background noise. That's why I brought up profiling. Again, for most of OFBiz (especially business logic) what it used won't make any significant difference. There may be a few places in the framework where things could be improved, but searching through the code for these trying to find patterns that _might_ perform worse than an alternative may make no change at all, or may even make things worse. Profiling will help you know if it really improved things, and will also help you find actual performance problems (memory use and execution time) instead of poking around in the dark. Once a performance problem is found, then you can start experimenting with changes that will improve things, and then some of these ideas might be helpful. Until then, it's great to share information but IMO it is not actionable at all (or wise to act on any way with profiling, unless you have time to kill and aren't concerned about the risk of doing more harm than good). -David > --- On Wed, 6/9/10, Scott Gray <scott.g...@hotwaxmedia.com> wrote: > >> From: Scott Gray <scott.g...@hotwaxmedia.com> >> Subject: Re: Discussion: When To Use Javolution (was: EntityCondition >> factory objects) >> To: dev@ofbiz.apache.org >> Date: Wednesday, June 9, 2010, 11:56 PM >> Interesting post but what I'm not >> hearing is any mention of specific downsides to using >> javolution in place of the util classes even when the use >> may not be taking advantage of any specific javolution >> features. >> >> You mention this: >>> There is no performance benefit to using FastList in >> this scenario. An ArrayList will use less memory and will >> perform faster than FastList - if its size is initialized to >> the correct value. Better yet, if you know the number of >> objects in advance, then just create an array. >> >> But you provide no evidence to back the statement up. >> And a FastList can also be given an initial size. >> >> I'm disagreeing with what you're saying because I really >> don't know much about it, but your post doesn't really do >> much to increase my knowledge or give me any reason to >> follow your advice. >> >> Regards >> Scott >> >> HotWax Media >> http://www.hotwaxmedia.com >> >> On 10/06/2010, at 6:25 PM, Adrian Crum wrote: >> >>> I'm continuing this discussion with a new subject >> since the thread is starting to diverge from the original >> subject. >>> >>> A lot of the current code uses Javolution classes in >> many places for one common reason - copy-and-paste >> development. If you don't understand the Javolution library >> and its intended use and actual benefits then it's hard to >> know when the classes should be used and when there might be >> better alternatives. >>> >>> When I see class names like FastList and FastMap, I >> assume using them will speed up code. Indeed, some JRE class >> methods will execute faster using Javolution instead of JRE >> classes, and those methods are well documented on the >> Javolution website. If a bit of code doesn't use any of >> those methods, then there will be no benefit to using >> Javolution. >>> >>> Adam and I discussed earlier the use of object pools. >> Object pools used to improve performance because they helped >> cut down on garbage collection. Sun/Oracle recommends >> getting rid of object pools when using the newer versions of >> Java because the newer versions have improved garbage >> collectors. >>> >>> If you do a Google search for "java performance >> improvement" you'll get a lot of links to a lot of articles. >> From my experience a lot of those ideas are based on some >> special knowledge of how the JVM works and they "game the >> system" to improve performance. As a result, some of those >> optimizations depend on the JVM version and the platform it >> runs on. >>> >>> My preference is to use efficient algorithms and well >> structured code, and leave the performance optimizations to >> the JVM. I can give an example that will be obvious to >> everyone: >>> >>> Let's say a section of code builds a List of objects >> and then iterates over the List. Once the List is created, >> its contents don't change - there are no additions, >> removals, inserts, etc. In addition, this List will be a >> member of an object that is kept in a cache. >>> >>> There is no performance benefit to using FastList in >> this scenario. An ArrayList will use less memory and will >> perform faster than FastList - if its size is initialized to >> the correct value. Better yet, if you know the number of >> objects in advance, then just create an array. >>> >>> If an ArrayList is used, you can call the trimToSize >> method after the List is filled to reduce the memory it >> uses. Better yet, convert it to an array to reduce memory >> use even more. A cached object that contains an array >> instead of FastList will take less memory and perform >> better. >>> >>> So, the main idea is to think about how the collection >> is being used and then choose the best class for it. Don't >> assume a Javolution class will always perform better. >>> >>> By the way, I'm not pointing any fingers or talking >> down to anyone here. I've done the copy-and-paste >> development myself. It's only recently that I started to >> scrutinize my choice of classes. >>> >>> -Adrian >>> >>> >>> --- On Wed, 6/9/10, Adrian Crum <adrian.c...@yahoo.com> >> wrote: >>>> --- On Wed, 6/9/10, David E Jones >>>> <d...@me.com> >>>> wrote: >>>>> On Jun 9, 2010, at 4:56 PM, Adrian Crum >> wrote: >>>>> >>>>>> On 6/9/2010 3:44 PM, Adam Heath wrote: >>>>>>> Adrian Crum wrote: >>>>>>>> I remember when Javolution was >> first >>>> brought >>>>> into the project. The >>>>>>>> reason for adding it was better >>>> performance. I >>>>> was new to the project at >>>>>>>> the time, so I just assumed that >> was >>>> true. >>>>>>>> >>>>>>>> Since then I have read many books >> and >>>> articles >>>>> on Java, and now I'm not >>>>>>>> sure that Javolution is >> appropriate for >>>> this >>>>> project. >>>>>>> >>>>>>> I've also had doubts about >>>>> FastMap(javolution). It doesn't >> implement >>>>>>> ConcurrentMap; the putIfAbsent method >> it >>>> *does* >>>>> implement is not >>>>>>> completely defined. >>>>>>> >>>>>>> FastSet/FastMap don't have a defined >>>> order. >>>>> It appears to be linked, >>>>>>> when no Comparator is used, but that >> is not >>>> well >>>>> defined. >>>>>>> >>>>>>> javolution itself is supposed to be >> defined >>>> as >>>>> being more consistent >>>>>>> in memory usage and performance. >> The >>>> library >>>>> says these are useful >>>>>>> when the target platform is an >> embedded >>>>> environment. However, ofbiz >>>>>>> is not really an embedded-type >>>> application. >>>>> The extra overhead that >>>>>>> javolution uses for maintain memory >> block >>>> areas >>>>> makes it very hard for >>>>>>> the jvm to do the new fancy escape >> analysis. >>>>>>> Lots of places in ofbiz use >>>>> FastMap/List/Set. They are not useful, >>>>>>> however, in places that only get >> populated >>>> at >>>>> startup, and never ever >>>>>>> changed thereafter. I've started >> fixing >>>> some >>>>> of these use cases as I >>>>>>> spot them. >>>>>> >>>>>> I've used arrays instead of Lists in >> similar >>>> cases. We >>>>> really should have a discussion about this. >> Using >>>> Javolution >>>>> by default in a shotgun attempt to improve >> performance >>>> is >>>>> not a good strategy, in my opinion. >>>>> >>>>> I agree. If I understand correctly are you >> saying that >>>> the >>>>> move away from javolution will NOT be done as >> a >>>> shotgun >>>>> attempt to improve performance? >>>> >>>> Correct. Any changes that are made should be for a >> good >>>> reason. >>>> >>>> -Adrian >>>> >>>> >>>> >>>> >>>> >>> >>> >>> >> >> > > >
