Listen, I really don't have time to waste explaining to you how to do proper benchmarks in a Hotspot-style JVM! But, for a start, any tests _not_ done in a loop are absolutely meaningless!
In my *much* more scientific tests, I find that the flush time per object is about 0.01ms (about 1/7th of what you are claiming, which is already much less than you were claiming before). Now, this can be affected by the size of the actual objects we are talking about but your numbers still seem high.
Now, lets get back to reality.
For the objects I mentioned above, the actual cost of loading them from the database in the first place is about 0.13ms per object on a local Oracle database . So this falls _well_ within our claimed <10% overhead.
OTOH, for nontrivial problems, the performance optimizations that Hibernate can make, which are very difficult to make in handcoded JDBC, can save you _orders_of_magnitude_ in some transactions!
Gavin.
jiesheng zhang wrote:
Hi, I once suspect that hibernate take too much time in
doing dirty check during session flush. However Gavin
king and other hibernate-user disagreed with me.
I did a simple performance testing to verify the dirty
check performance.
My conslusion is that the performance is not so good if there are many objects in session. If a session has around 1000 objects in memory, only will the dirty check take about 200 million second. For detailed performance metrics, see the table below.
The structure of my testing object is very simple. One thing I am not sure is whether the dirty checking algorithm is related to object structure or not. If it is, the dirty check in reality will take more time.
My testing case is attached.
---------------test logic ----------------
1. load some (n) number of objects in memory.
2. begin tranaction.
3. // do not do anything here.
4. commit.
Then calculate the time consumed from step 2 and 4.
---------------- test code ----------------- List ps=new ArrayList(10010); for (int i=1000; i<2100; i++) { Parent p1=(Parent)session.load(Parent.class, new Long(i)); p1.getValues().size(); } long startTime=System.currentTimeMillis(); Transaction tx=session.beginTransaction(); tx.commit(); long endTime=System.currentTimeMillis(); System.out.println("total time(in ms):"+(endTime-startTime));
-------------The performance metics--------- objects in memory time (in ms) for dirty check (3 experiments) 10000 741, 751,821 2000 200, 230, 230 1000 201, 191, 190, 100 30, 30, 30 1 10, 10, 10
jason
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