Akka.Streams.Kafka v1.5.39-beta3 benchmark results

PlainPartitionSourceBenchmarks.md

BenchmarkDotNet v0.14.0, Pop!_OS 22.04 LTS
13th Gen Intel Core i7-1360P, 1 CPU, 16 logical and 12 physical cores
.NET SDK 9.0.100
  [Host]  : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2
  LongRun : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2

Job=LongRun  EvaluateOverhead=False  Concurrent=True
Server=True  InvocationCount=1  IterationCount=10
LaunchCount=3  RunStrategy=Monitoring  UnrollFactor=1
WarmupCount=3

Method	PollBatchSize	Mean	Error	StdDev	msg/sec
ConsumeMessageAsync	10	NA	NA	NA	<not found>
ConsumeMessageAsync	100	NA	NA	NA	<not found>
ConsumeMessageAsync	500	169.3 μs	0.82 μs	1.23 μs	5,906.44

PlainSourceBenchmark.md

                                                                                                             
BenchmarkDotNet v0.14.0, Pop!_OS 22.04 LTS                                                                   
13th Gen Intel Core i7-1360P, 1 CPU, 16 logical and 12 physical cores                                        
.NET SDK 9.0.100                                                                                             
  [Host]  : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2                                                       
  LongRun : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2                                                       
                                                                                                             
Job=LongRun  EvaluateOverhead=False  Concurrent=True                                                         
Server=True  InvocationCount=1  IterationCount=10                                                            
LaunchCount=3  RunStrategy=Monitoring  UnrollFactor=1                                                        
WarmupCount=3                                                                                                
                                                                                                             

Method	PollBatchSize	Mean	Error	StdDev	msg/sec
ConsumeMessageAsync	10	78.58 μs	3.662 μs	5.481 μs	12,725.75
ConsumeMessageAsync	100	46.44 μs	2.329 μs	3.486 μs	21,533.17
ConsumeMessageAsync	500	42.31 μs	2.553 μs	3.821 μs	23,637.83

IMHO, I think the MergeHub we're using in the partitioned benchmarks is a source of performance issues - the component takes A LONG TIME to start under some conditions. I think we must be running into akkadotnet/akka.net#7253 (but for MergeHub, not BroadcastHub. Even with only ~3 publishers this makes me wonder if there's something off with the hub design there.