[jira] [Commented] (SPARK-13352) BlockFetch does not scale well on large block

["Davies Liu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-13352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15176589#comment-15176589 ] 

Davies Liu commented on SPARK-13352:
------------------------------------

[~rxin] Can someone help to look into this one?

This is one of the reasons broadcast hash join is slow with large broadcast.

> BlockFetch does not scale well on large block
> ---------------------------------------------
>
>                 Key: SPARK-13352
>                 URL: https://issues.apache.org/jira/browse/SPARK-13352
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>            Reporter: Davies Liu
>
> BlockManager.getRemoteBytes() perform poorly on large block
> {code}
>   test("block manager") {
>     val N = 500 << 20
>     val bm = sc.env.blockManager
>     val blockId = TaskResultBlockId(0)
>     val buffer = ByteBuffer.allocate(N)
>     buffer.limit(N)
>     bm.putBytes(blockId, buffer, StorageLevel.MEMORY_AND_DISK_SER)
>     val result = bm.getRemoteBytes(blockId)
>     assert(result.isDefined)
>     assert(result.get.limit() === (N))
>   }
> {code}
> Here are runtime for different block sizes:
> {code}
> 50M            3 seconds
> 100M          7 seconds
> 250M          33 seconds
> 500M         2 min
> {code}



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