[jboss-dev-forums] [Design of Messaging on JBoss (Messaging/JBoss)] - ByteBuffer.allocateDirect ridiculously

[clebert.suconic@jboss.com]

I just found out ByteBuffer.allocateDirect is ridiculously slow, that's why the Buffer reuse on Journal made a lot of difference on the performance for us.


  |    final int TIMES = 50;
  | 
  |    final long numberOfIteractions = 1000000;
  | 
  | 
  |    public void testJustAllocateBufferDirect() throws Exception
  |    {
  | 
  |       long start = System.currentTimeMillis();
  | 
  |       for (int c = 0; c < TIMES; c++)
  |       {
  |          for (long i = 0; i < numberOfIteractions; i++)
  |          {
  |             if (i == 10000)
  |             {
  |                start = System.currentTimeMillis();
  |             }
  |             MessagingBuffer bufferSend = ChannelBuffers.wrappedBuffer(ByteBuffer.allocateDirect(1024));
  |             
  |             bufferSend.writeBytes(new byte[1024]);
  |          }
  | 
  |          long spentTime = System.currentTimeMillis() - start;
  | 
  |          System.out.println("Time BuffersDirect = " + spentTime);
  |       }
  | 
  |    }
  |    
  |    public void testOurBuffers() throws Exception
  |    {
  | 
  |       long start = System.currentTimeMillis();
  | 
  |       for (int c = 0; c < TIMES; c++)
  |       {
  |          for (long i = 0; i < numberOfIteractions; i++)
  |          {
  |             if (i == 10000)
  |             {
  |                start = System.currentTimeMillis();
  |             }
  |             ChannelBuffer bufferSend = ChannelBuffers.wrappedBuffer(AsynchronousFileImpl.newNativeBuffer(1024));
  |             
  |             bufferSend.writeBytes(new byte[1024]);
  |             
  |             AsynchronousFileImpl.destroyBuffer(bufferSend.toByteBuffer());
  |          }
  | 
  |          long spentTime = System.currentTimeMillis() - start;
  | 
  |          System.out.println("Time JBM JNI Buffers = " + spentTime);
  |       }
  | 
  | 


On the Above test, ByteBuffer.allocateDirect needed 100 seconds to complete the 1 million buffers.

While our code, allocating ByteBuffers directly through JNI, needed 2 seconds to complete 1 million buffers.


That *is* ridiculous. 


The new Buffers were slicing the direct ByteBuffer, what affected the capacity, breaking buffer reuse, what raised this issue to my eyes.

I have made a few changes on the Journal, where we will allocate buffers directly, and I could get very good numbers with some simple tests. (Even thought I was not targeting any optimizations.. just looking after this bug on ByteBuffer).

We can talk about this tomorrow on the meeting.

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