commons-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COMPRESS-388) Improve concurrent reads from ZipFile
Date Sun, 23 Apr 2017 16:15:04 GMT

    [ https://issues.apache.org/jira/browse/COMPRESS-388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15980453#comment-15980453
] 

ASF GitHub Bot commented on COMPRESS-388:
-----------------------------------------

Github user sebbASF commented on a diff in the pull request:

    https://github.com/apache/commons-compress/pull/21#discussion_r112838372
  
    --- Diff: src/main/java/org/apache/commons/compress/archivers/zip/ZipFile.java ---
    @@ -1111,14 +1122,11 @@ public int read() throws IOException {
                     }
                     return -1;
                 }
    -            synchronized (archive) {
    -                archive.position(loc++);
    -                int read = read(1);
    -                if (read < 0) {
    -                    return read;
    -                }
    -                return buffer.get() & 0xff;
    +            int read = read(loc++, 1);
    +            if (read < 0) {
    --- End diff --
    
    Surely the increment of loc needs to be synchronised?


> Improve concurrent reads from ZipFile
> -------------------------------------
>
>                 Key: COMPRESS-388
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-388
>             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).



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)

Mime
View raw message