ASF GitHub Bot commented on IO-468:

Github user berndhopp closed the pull request at:


> 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
>              Labels: newbie, performance
>         Attachments: PerfTest.java, micro-benchmark.zip, 
> monitoring_with_threadlocals.png, monitoring_without_threadlocals.png, 
> performancetest.ods, performancetest_weakreference.ods
>   Original Estimate: 12h
>  Remaining Estimate: 12h
> 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 
> 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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