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From "Bernd Hopp (JIRA)" <j...@apache.org>
Subject [jira] [Created] (IO-468) Avoid allocating memory for method internal buffers, use threadlocal memory instead
Date Tue, 03 Feb 2015 07:51:34 GMT
Bernd Hopp created IO-468:
-----------------------------

             Summary: Avoid allocating memory for method internal buffers, use threadlocal
memory instead
                 Key: IO-468
                 URL: https://issues.apache.org/jira/browse/IO-468
             Project: Commons IO
          Issue Type: Improvement
          Components: Utilities
    Affects Versions: 2.4
         Environment: all environments
            Reporter: Bernd Hopp
            Priority: Minor
             Fix For: 2.5


In a lot of places, we allocate new buffers dynamically via new byte[]. This is a performance
drawback since many of these allocations could be avoided if we would use threadlocal buffers
that can be reused. For example, consider the following code from IOUtils.java, ln 2177:

return copyLarge(input, output, inputOffset, length, new byte[DEFAULT_BUFFER_SIZE]);

This code allocates new memory for every copy-process, that is not used outside of the method
and could easily and safely reused, as long as is is thread-local. So instead of allocating
new memory, a new utility-class could provide a thread-local bytearray like this:

byte[] buffer = ThreadLocalByteArray.ofSize(DEFAULT_BUFFER_SIZE);

return copyLarge(input, output, inputOffset, length, buffer);

I have not measured the performance-benefits yet, but I would expect them to be significant,
especially when the streams itself are not the performance bottleneck. 

Git PR is at https://github.com/apache/commons-io/pull/6/files



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