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From "Luke Lu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9194) RPC Support for QoS
Date Tue, 19 Mar 2013 18:09:17 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13606610#comment-13606610
] 

Luke Lu commented on HADOOP-9194:
---------------------------------

Thanks for the patch, Junping! A few things:

# Service level and service class are orthogonal concepts. Different QoS algos (our current
one is basically best effort) can achieve different service level even for the same service
class. The field is really CoS (class of service) analogous to the DiffServ field in IP see
http://www.linktionary.com/q/qos.html and http://www.linktionary.com/d/diffserv.html for details.
# Make the service class a connection member variable at the server side as well.
# Add getter/setter for the service class to facilitate testing and future usage.
# Add a basic test to make sure the service class is being serialized/transmitted correctly.
                
> RPC Support for QoS
> -------------------
>
>                 Key: HADOOP-9194
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9194
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: ipc
>    Affects Versions: 2.0.2-alpha
>            Reporter: Luke Lu
>         Attachments: HADOOP-9194.patch
>
>
> One of the next frontiers of Hadoop performance is QoS (Quality of Service). We need
QoS support to fight the inevitable "buffer bloat" (including various queues, which are probably
necessary for throughput) in our software stack. This is important for mixed workload with
different latency and throughput requirements (e.g. OLTP vs OLAP, batch and even compaction
I/O) against the same DFS.
> Any potential bottleneck will need to be managed by QoS mechanisms, starting with RPC.

> How about adding a one byte DS (differentiated services) field (a la the 6-bit DS field
in IP header) in the RPC header to facilitate the QoS mechanisms (in separate JIRAs)? The
byte at a fixed offset (how about 0?) of the header is helpful for implementing high performance
QoS mechanisms in switches (software or hardware) and servers with minimum decoding effort.

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