GitHub user liyezhang556520 opened a pull request:
https://github.com/apache/spark/pull/12296
[SPARK-14290][CORE][backport-1.6] avoid significant memory copy in Netty's
tranâ¦
## What changes were proposed in this pull request?
When netty transfer data that is not `FileRegion`, data will be in format
of `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.
In this PR, if data size is large, we will split it into small chunks to
call `WritableByteChannel.write()`, so that avoid wasting of memory copy.
Because the data can't be written within a single write, and it will call
`transferTo` multiple times.
## How was this patch tested?
Spark unit test and manual test.
Manual test:
`sc.parallelize(Array(1,2,3),3).mapPartitions(a=>Array(new
Array[Double](1024 * 1024 * 50)).iterator).reduce((a,b)=> a).length`
For more details, please refer to
[SPARK-14290](https://issues.apache.org/jira/browse/SPARK-14290)
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/liyezhang556520/spark
apache-branch-1.6-spark-14290
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/12296.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #12296
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commit 9e37e7c4d1e495da91f68e912636dcf865691e39
Author: Zhang, Liye <[email protected]>
Date: 2016-04-11T08:05:44Z
SPARK-14290/SPARK-13352 avoid significant memory copy in Netty's transferTo
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