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Date: Wed, 2 Mar 2011 08:17:57 -0800
Message-ID: <AANLkTikaHFUBs+LUdvDSLL2Ff2iinRNg=SQZ3aN_Shtv@mail.gmail.com>
Subject: Re: Is DFSInputStream.read(long position,...) designed for multi
 threaded access?
From: Jason Rutherglen <jason.rutherglen@gmail.com>
To: Todd Lipcon <todd@cloudera.com>
Cc: hdfs-user@hadoop.apache.org
Content-Type: text/plain; charset=ISO-8859-1

Todd,

Thanks for the reply.  I looked at HDFS-941 which seems to remove the
redundant creation of BlockReaders.  That and HDFS-347 will solve some
of the issues, however I think there's also the sendmsg() of the file
descriptor that also needs to be implemented?

Jason

On Tue, Mar 1, 2011 at 5:58 PM, Todd Lipcon <todd@cloudera.com> wrote:
> Hi Jason,
>
> Yes, this method is currently very inefficient.. HDFS-941 will
> hopefully improve this situation, but currently there's no
> particularly efficient way to do multithreaded random access.
>
> -Todd
>
> On Tue, Mar 1, 2011 at 4:24 PM, Jason Rutherglen
> <jason.rutherglen@gmail.com> wrote:
>> It's unsynchronized however it's creating a new BlockReader on each
>> call, that seems like a problem?
>>
>
>
>
> --
> Todd Lipcon
> Software Engineer, Cloudera
>