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From Jeanfrancois Arcand <jfarc...@apache.org>
Subject Re: Is MINA ByteBuffer pool of dubious value?
Date Fri, 17 Nov 2006 21:38:45 GMT
Hi,

Trustin Lee wrote:
> Hi,
> 
> I ran some performance test with the following settings:
> 
> * Direct buffer with PooledByteBufferAllocator
> * Heap buffer with PooledByteBufferAllocator
> * Heap buffer with SimpleByteBufferAllocator
> 
> PooledByteBufferAllocator is the default allocator that MINA uses to
> allocate ByteBuffers.  It pools all buffers created by itself.  When a user
> calls ByteBuffer.release(), it is returned to the pool.  MINA is 
> implemented
> to release the buffer automatically for a few obvious case as specified in
> JavaDoc.  The reason why I introduced the pool and acquire/release() 
> methods
> is because direct buffers take long time to be allocated.  By using buffer
> pooling, we were able to save time to allocate direct ByteBuffers.  The
> disadvantage of this allocator is that there's synchronization cost during
> acquire() or release() is invoked.  It might prevent multi-processor
> machines from performing better than we expected.
> 
> SimpleByteAllocator is a very simple allocator.  It just creates a new
> ByteBuffer whenever requested.  It never pools anything.  The advantage of
> this allocator is that it doesn't have any synchronization cost.  It just
> allocates a buffer and forget about it.  This works best with heap byte
> buffers because the time complexity of Java heap memory allocation is O(1),
> fantastic constant time.
> 
> We usually have been taught that direct buffers will perform better than
> heap buffers, but many performance test results including mine are saying
> that heap buffers are performing *far* better.  I got almost 50% 
> performance
> boost after switching from direct buffer with PooledByteBufferAllocator to
> heap buffer with SimpleByteBufferAllocator.  Is there anyone who had 
> similar
> experiences?

Yes I've found the same result.

> 
> In this context, I think the value of the default buffer pooling that MINA
> provides might be dubious.  If this is true, should we have to have
> acquire() and release() methods sacrificing API usability?  Why don't we
> just get rid of (or deprecate) them and let the VM take care of the whole
> buffer management?

One thing you might consider is to create a very large direct ByteBuffer 
and slice it in your PooledByteBufferAllocator. Clients of 
PooledByteBufferAllocator will not see any difference, but the 
performance might significantly improve (might be better that Heap 
Buffer). You might consider doing the trick for heap as well.

Thanks

-- Jeanfrancois



> 
> Trustin
> 
> PS: I beat Apache HTTP 2.0.55 with MINA + AsyncWeb today.  I was able to 
> get
> 20,000 msg/sec throughput with my dual core opteron dual box.  I will give
> you an update later when more data is gathered and feel confident that I
> configured Apache HTTPD to its maximum performance.

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