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

["Ivan Vergiliev (JIRA)" <ji...@apache.org>]

Ivan Vergiliev created SPARK-5269:
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             Summary: 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


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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