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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IO-468) Avoid allocating memory for method internal buffers, use threadlocal memory instead
Date Wed, 04 Feb 2015 16:10:40 GMT

    [ https://issues.apache.org/jira/browse/IO-468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14305390#comment-14305390
] 

Sebb commented on IO-468:
-------------------------

Where is the new patch?

Note that with the current code, the memory is released when the method exits.

Whereas with a ThreadLocal implementation the memory won't be released until some time after
the thread exits.

Note that the IOUtils class already has versions of the methods that allow the user to provide
the buffer.
So users that want to re-use buffers can already do so.

> 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
>             Fix For: 2.5
>
>   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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