sanastas commented on issue #7676: Add OakIncrementalIndex to Druid
URL: https://github.com/apache/incubator-druid/pull/7676#issuecomment-503631910
 
 
   Hi Slim (@b-slim ),
   
   We have taken your comment about Netty Allocator seriously and implemented 
and measured OakIncrementalIndex performance based on Netty. The comparison was 
running IncrementalIngestionBenchmark and inserting 3 million rows which is 
about 3.8GGB of off-heap data. We have tried giving different off-heap size 
limits, the result can be seen in the following table.
   
   [Oak Native Allocator vs 
Netty.pdf](https://github.com/apache/incubator-druid/files/3306983/Oak.Native.Allocator.vs.Netty.pdf)
   
   To summarize, Netty Allocator requires up to twice memory and when its 
memory request is satisfied the latency is a bit slower. Looking closer on 
Netty implementation it is understandable, because Netty Allocator Pools hold 
buffers in different (exponentially increasing) sizes. This is reasonable for 
network protocol buffers but less reasonable for data storage.
   
   Bottom line, based on empirical results we would like to continue with the 
primitive OakNativeAllocator which satisfies the Druid needs and gives better 
performance. The experiments with Netty Allocator will continue. Thank you for 
you valuable input!
   
   
   

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