Use exponential backoff during job submission when ring buffers are full

Signed-off-by: Jeremy Ong <jcong@amazon.com>

Code/Framework/AzCore/AzCore/Jobs/JobExecutor.cpp

@@ -9,13 +9,14 @@
 #include <AzCore/Jobs/JobExecutor.h>
 #include <AzCore/Jobs/JobGraph.h>
 
-#include <AzCore/std/string/string.h>
 #include <AzCore/std/containers/queue.h>
 #include <AzCore/std/parallel/binary_semaphore.h>
-#include <AzCore/std/parallel/semaphore.h>
+#include <AzCore/std/parallel/exponential_backoff.h>
 #include <AzCore/std/parallel/mutex.h>
 #include <AzCore/std/parallel/scoped_lock.h>
+#include <AzCore/std/parallel/semaphore.h>
 #include <AzCore/std/parallel/thread.h>
+#include <AzCore/std/string/string.h>
 
 #include <random>
 
@@ -124,6 +125,7 @@ namespace AZ
             uint8_t priority = job->GetPriorityNumber();
             QueueStatus& status = m_status[priority];
 
+            AZStd::exponential_backoff backoff;
             while (true)
             {
                 uint16_t reserve = status.reserve.load();
@@ -153,8 +155,7 @@ namespace AZ
                 }
                 else
                 {
-                    // TODO need exponential backup here
-                    AZStd::this_thread::sleep_for(AZStd::chrono::microseconds{ 100 });
+                    backoff.wait();
                 }
             }
         }

Code/Framework/AzCore/Tests/JobGraphTests.cpp

@@ -565,7 +565,6 @@ namespace Benchmark
             graph->SubmitOnExecutor(*executor, &ev);
             ev.Wait();
         }
-        executor->Drain();
     }
 
     BENCHMARK_F(JobGraphBenchmarkFixture, FourToOneJoin)(benchmark::State& state)
@@ -596,7 +595,6 @@ namespace Benchmark
             graph->SubmitOnExecutor(*executor, &ev);
             ev.Wait();
         }
-        executor->Drain();
     }
 } // namespace Benchmark
 #endif