commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IO-468) Avoid allocating memory for method internal buffers, use threadlocal memory instead
Date Tue, 03 Feb 2015 13:32:34 GMT

    [ https://issues.apache.org/jira/browse/IO-468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14303254#comment-14303254
] 

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

AIUI memory allocation via new byte[] is not cpu-intensive.
Also the memory will be automatically returned when the method completes.

ThreadLocal has the issue that the memory is not automatically released when the thread no
longer needs it.

I had a quick look at the patch, and it also replaces the skip buffer with a thread local
buffer. Since skip buffers are write-only, that is completely unnecessary.

The patch also fails to release any of the buffers when they are no longer needed.

Without convincing evidence that using ThreadLocal for buffers signiificantly helps performance
without introducing memory leaks, I am against applying it.

> 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



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message