BenchmarkDotNet=v0.13.0, OS=Windows 10.0.18363.1316 (1909/November2019Update/19H2)
Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET SDK=5.0.300
  [Host]     : .NET 5.0.6 (5.0.621.22011), X64 RyuJIT
  DefaultJob : .NET 5.0.6 (5.0.621.22011), X64 RyuJIT
MethodMeanErrorStdDevRatioRatioSD
AwaitSeqDummyMonitor39.95 ms0.968 ms2.824 ms1.000.00
AwaitSeqSemaphoreSlim39.96 ms0.798 ms1.833 ms1.000.08
ParallelAwaitWhenAll15.88 ms0.317 ms0.883 ms0.400.03