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https://issues.apache.org/jira/browse/IO-355?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13488250#comment-13488250
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Uli Bubenheimer commented on IO-355:
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Was referring to the wrong methods. I meant the copyLarge() methods that call
IOUtils.skip() - Javadoc should say that the skip will not do a seek and may be
slower than they expect.
Preferably I hope you will consider changing the methods to have them call the
InputStream.skip() or Reader.skip() directly - I bet that 99.99% of the users
of these methods are not interested in the redefined skip() contract, but want
convenient methods to copy things from an input to an output while skipping
some data. They are most likely not interested in getting a bad deal on
performance.
Or add copyLargeFast() methods or something similar.
> IOUtils copyLarge() and skip() methods are performance hogs
> -----------------------------------------------------------
>
> Key: IO-355
> URL: https://issues.apache.org/jira/browse/IO-355
> Project: Commons IO
> Issue Type: Bug
> Components: Utilities
> Affects Versions: 2.3, 2.4
> Reporter: Uli Bubenheimer
>
> IOUtils.skip(InputStream, long) and IOUtils.skip(Reader, long) have the worst
> possible performance as they always use read() on the input instead of using
> skip(). In many cases, using skip() from a subclass of InputStream is much
> faster than read(), as the skip() can be implemented via a disk seek.
> The IOUtils.skip() methods are used in the read() methods of IOUtils and
> their similarly named siblings, so they tend to bring down the performance of
> all reads that involve a skip.
> Case in point: I have observed this performance degradation with Java 7 on
> Windows 7. A series of consecutive reads on a large file on disk that
> involved skips changed my performance from 30 secs as my baseline to 10
> minutes after starting to use IOUtils.read().
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