add EMode to WorkerTheadPool to avoid thread starvation (#492)

- Improvement: Add a new mode to worker thread pools to avoid starvation of workers which could cause long stalls due to other work begin queued up. UE-305498

1 files changed, 16 insertions, 13 deletions

diff --git a/src/zenserver/projectstore/projectstore.cpp b/src/zenserver/projectstore/projectstore.cpp
index 322af5e69..7cb115110 100644
--- a/src/zenserver/projectstore/projectstore.cpp
+++ b/src/zenserver/projectstore/projectstore.cpp
@@ -1704,7 +1704,7 @@ ProjectStore::Oplog::Validate(const std::filesystem::path& ProjectRootDir,
 
 	std::atomic<bool> AbortFlag;
 	std::atomic<bool> PauseFlag;
-	ParallelWork	  Work(AbortFlag, PauseFlag);
+	ParallelWork	  Work(AbortFlag, PauseFlag, WorkerThreadPool::EMode::DisableBacklog);
 	try
 	{
 		for (uint32_t OpIndex = 0; !IsCancelledFlag && OpIndex < Result.OpCount; OpIndex++)
@@ -2249,7 +2249,7 @@ ProjectStore::Oplog::IterateChunks(const std::filesystem::path&														  P
 	{
 		std::atomic<bool> AbortFlag;
 		std::atomic<bool> PauseFlag;
-		ParallelWork	  Work(AbortFlag, PauseFlag);
+		ParallelWork	  Work(AbortFlag, PauseFlag, WorkerThreadPool::EMode::DisableBacklog);
 		try
 		{
 			for (size_t ChunkIndex = 0; ChunkIndex < FileChunkIndexes.size(); ChunkIndex++)
@@ -4122,21 +4122,24 @@ ProjectStore::Flush()
 	WorkerThreadPool& WorkerPool = GetSmallWorkerPool(EWorkloadType::Burst);
 	std::atomic<bool> AbortFlag;
 	std::atomic<bool> PauseFlag;
-	ParallelWork	  Work(AbortFlag, PauseFlag);
+	ParallelWork	  Work(AbortFlag, PauseFlag, WorkerThreadPool::EMode::DisableBacklog);
 	try
 	{
 		for (const Ref<Project>& Project : Projects)
 		{
-			Work.ScheduleWork(WorkerPool, [this, Project](std::atomic<bool>&) {
-				try
-				{
-					Project->Flush();
-				}
-				catch (const std::exception& Ex)
-				{
-					ZEN_WARN("Exception while flushing project {}: {}", Project->Identifier, Ex.what());
-				}
-			});
+			Work.ScheduleWork(
+				WorkerPool,
+				[this, Project](std::atomic<bool>&) {
+					try
+					{
+						Project->Flush();
+					}
+					catch (const std::exception& Ex)
+					{
+						ZEN_WARN("Exception while flushing project {}: {}", Project->Identifier, Ex.what());
+					}
+				},
+				0);
 		}
 	}
 	catch (const std::exception& Ex)