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https://issues.apache.org/jira/browse/HDFS-5541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13841905#comment-13841905
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Colin Patrick McCabe commented on HDFS-5541:
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By the way, thanks for looking at these issues. I realize libhdfs can be a
little intimidating when you first look at it, but it's actually simpler than
it looks. If you have any questions, even if they seem trivial, you should
post them hdfs-dev, and we'll try to answer as best we can. Probably a lot of
other people have the same question.
Another thing I would kind of like to see is the Windows build using CMake.
That would avoid the need to manually generate vcproj files and maintain two
sets of build information files. Windows support for libhdfs might be a good
trial run for this.
> LIBHDFS questions and performance suggestions
> ---------------------------------------------
>
> Key: HDFS-5541
> URL: https://issues.apache.org/jira/browse/HDFS-5541
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Reporter: Stephen Bovy
> Priority: Minor
> Attachments: pdclibhdfs.zip
>
>
> Since libhdfs is a "client" interface", and esspecially because it is a "C"
> interface , it should be assumed that the code will be used accross many
> different platforms, and many different compilers.
> 1) The code should be cross platform ( no Linux extras )
> 2) The code should compile on standard c89 compilers, the
> >>> {least common denominator rule applies here} !! <<
> C code with "c" extension should follow the rules of the c standard
> All variables must be declared at the begining of scope , and no (//)
> comments allowed
> >> I just spent a week white-washing the code back to nornal C standards so
> >> that it could compile and build accross a wide range of platforms <<
> Now on-to performance questions
> 1) If threads are not used why do a thread attach ( when threads are not used
> all the thread attach nonesense is a waste of time and a performance killer )
> 2) The JVM init code should not be imbedded within the context of every
> function call . The JVM init code should be in a stand-alone LIBINIT
> function that is only invoked once. The JVM * and the JNI * should be
> global variables for use when no threads are utilized.
> 3) When threads are utilized the attach fucntion can use the GLOBAL jvm *
> created by the LIBINIT { WHICH IS INVOKED ONLY ONCE } and thus safely
> outside the scope of any LOOP that is using the functions
> 4) Hash Table and Locking Why ?????
> When threads are used the hash table locking is going to hurt perfromance .
> Why not use thread local storage for the hash table,that way no locking is
> required either with or without threads.
>
> 5) FINALLY Windows Compatibility
> Do not use posix features if they cannot easilly be replaced on other
> platforms !!
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