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https://issues.apache.org/jira/browse/HADOOP-9194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13549281#comment-13549281
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Colin Patrick McCabe commented on HADOOP-9194:
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Hi Luke,
Interesting idea.
You mention DiffServ (internet protocol differentiated services) in your
description. Is there a reason we need our own fields, if the same information
is present in DiffServ? It seems like if the switch hardware supports
DiffServ, it is unnecessary to have our own field in the RPC header. On the
other hand, if the hardware doesn't support DiffServ, adding our own byte will
do no good. Am I missing something here?
(Note that I'm not arguing against having QoS-related fields in general in
protobuf messages, just questioning whether it makes sense to put them in the
RPC header.)
> 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
>
> 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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