[jira] [Commented] (SPARK-5269) BlockManager.dataDeserialize always creates a new serializer instance

["Matt Cheah (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-5269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14630783#comment-14630783 ] 

Matt Cheah commented on SPARK-5269:
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I'd be interested in working on this with [~vladio]. Can this be assigned to either of us?

> BlockManager.dataDeserialize always creates a new serializer instance
> ---------------------------------------------------------------------
>
>                 Key: SPARK-5269
>                 URL: https://issues.apache.org/jira/browse/SPARK-5269
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>            Reporter: Ivan Vergiliev
>              Labels: performance, serializers
>
> BlockManager.dataDeserialize always creates a new instance of the serializer, which is pretty slow in some cases. I'm using Kryo serialization and have a custom registrator, and its register method is showing up as taking about 15% of the execution time in my profiles. This started happening after I increased the number of keys in a job with a shuffle phase by a factor of 40.
> One solution I can think of is to create a ThreadLocal SerializerInstance for the defaultSerializer, and only create a new one if a custom serializer is passed in. AFAICT a custom serializer is passed only from DiskStore.getValues, and that, on the other hand, depends on the serializer passed to ExternalSorter. I don't know how often this is used, but I think this can still be a good solution for the standard use case.
> Oh, and also - ExternalSorter already has a SerializerInstance, so if the getValues method is called from a single thread, maybe we can pass that directly?
> I'd be happy to try a patch but would probably need a confirmation from someone that this approach would indeed work (or an idea for another).



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