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From "Zbynek Vyskovsky (JIRA)" <>
Subject [jira] [Created] (COMPRESS-388) Improve concurrent reads from ZipFile
Date Sun, 23 Apr 2017 06:45:04 GMT
Zbynek Vyskovsky created COMPRESS-388:

             Summary: Improve concurrent reads from ZipFile
                 Key: COMPRESS-388
             Project: Commons Compress
          Issue Type: Improvement
          Components: Archivers
    Affects Versions: 1.13
         Environment: Any
            Reporter: Zbynek Vyskovsky
             Fix For: 1.14

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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