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From "Zbynek Vyskovsky (JIRA)" <>
Subject [jira] [Commented] (COMPRESS-388) Improve concurrent reads from ZipFile
Date Mon, 24 Apr 2017 19:58:04 GMT


Zbynek Vyskovsky commented on COMPRESS-388:

If you mean the proposal about exposing the offset and length, than no, this is independent.
I can create another issue for this.

> Improve concurrent reads from ZipFile
> -------------------------------------
>                 Key: COMPRESS-388
>                 URL:
>             Project: Commons Compress
>          Issue Type: Improvement
>          Components: Archivers
>    Affects Versions: 1.13
>         Environment: Any
>            Reporter: Zbynek Vyskovsky
>              Labels: patch, performance
>             Fix For: 1.14
>   Original Estimate: 2h
>  Remaining Estimate: 2h
> Concurrent reads on the ZipFile archive is terribly slow on multiprocessor systems. On
my 4 CPU laptop it shows 26 reads/s vs 2 reads/s on 100MB samples for example.
> The cause is the use of synchronized blocks to access the underlying file channel. This
may be required for generic SeekableByteChannel but most commonly there is FileChannel implementation
which supports lock-free reading from any position (i.e. using pread/pwrite system calls or
their equivalent).
> With the fix the performance is about 10 times faster (on 4 CPU system, with more processor
the difference should grow significantly).

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