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Date: Mon, 9 Mar 2015 00:48:38 +0000 (UTC)
From: "Sebb (JIRA)" <jira@apache.org>
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Subject: [jira] [Resolved] (IO-468) Avoid allocating memory for method
 internal buffers, use threadlocal memory instead
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     [ https://issues.apache.org/jira/browse/IO-468?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sebb resolved IO-468.
---------------------
       Resolution: Won't Fix
    Fix Version/s:     (was: 2.5)

> 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 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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