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From Steve Ulrich <steve.ulr...@proemion.com>
Subject Re: Interesting direct buffer vs heap buffer micro benchmark
Date Mon, 07 Apr 2008 07:00:06 GMT
"이희승 (Trustin Lee <trustin@...> writes:

> Emmanuel Lecharny wrote:
> It seems like the hotspot engine optimizes the test(...) method to work
> better with a certain type of byte buffer.  I inlined the test(...)
> method into the two test methods, and now I am getting consistent
> result.  Direct buffer outperforms heap buffer for all cases in Java 6,
> except for the allocation and deallocation.  If we can provide
> reasonable solution for pooling direct buffers, we will be able to gain
> more performance out of MINA.
> 
> BTW, it is interesting that direct buffer outperforms heap buffer.
> Kudos to the JVM developers!


Hi! I did some testing just a while back. I got similar results and read the
javadoc more carefully, which states some points about "direct" buffers:
- They are expensive to create.
- They can prevent that a java byte buffer is copied to a native array/buffer in
an IO-Operation.
"It is therefore recommended that direct buffers be allocated primarily for
large, long-lived buffers that are subject to the underlying system's native I/O
operations."

Your test is therefore missing some "IO action" where a direct/heap buffer can
do it's tricks.

Mina is an IO-Framework, so there may be some places that will perform better
with direct buffers and some places where a pure java buffer does. The question
is: How much can you increase performance with tweaking the buffers without
harming the performance in some worst case scenarios (i.e. small messages vs.
big messages).



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