Zhang, Liye created SPARK-14290:
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Summary: Fully utilize the network bandwidth for Netty RPC by
avoid significant underlying memory copy
Key: SPARK-14290
URL: https://issues.apache.org/jira/browse/SPARK-14290
Project: Spark
Issue Type: Improvement
Components: Input/Output, Spark Core
Affects Versions: 1.6.0, 1.5.0, 1.4.0, 1.3.0, 1.2.0, 2.0.0
Reporter: Zhang, Liye
When netty transfer data that is not from `FileRegion`, data will be transfered
as `ByteBuf`, If the data is large, there will occur significant performance
issue because there is memory copy underlying in `sun.nio.ch.IOUtil.write`, the
CPU is 100% used, and network is very low. We can check it by comparing `NIO`
and `Netty` for`spark.shuffle.blockTransferService` in spark 1.4. NIO network
bandwidth is much better than Netty.
How to reproduce:
{code}
sc.parallelize(Array(1,2,3),3).mapPartitions(a=>Array(new Array[Double](1024 *
1024 * 50)).iterator).reduce((a,b)=> a).length
{code}
The root cause can referred
[here|http://stackoverflow.com/questions/34493320/how-does-buffer-size-affect-nio-channel-performance].
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