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, 4 insertions, 3 deletions

diff --git a/src/zenstore/cache/cachedisklayer.cpp b/src/zenstore/cache/cachedisklayer.cpp
index cacbbd966..fd52cdab5 100644
--- a/src/zenstore/cache/cachedisklayer.cpp
+++ b/src/zenstore/cache/cachedisklayer.cpp
@@ -4215,7 +4215,7 @@ ZenCacheDiskLayer::DiscoverBuckets()
 	WorkerThreadPool& Pool = GetLargeWorkerPool(EWorkloadType::Burst);
 	std::atomic<bool> AbortFlag;
 	std::atomic<bool> PauseFlag;
-	ParallelWork	  Work(AbortFlag, PauseFlag);
+	ParallelWork	  Work(AbortFlag, PauseFlag, WorkerThreadPool::EMode::DisableBacklog);
 	try
 	{
 		for (auto& BucketPath : FoundBucketDirectories)
@@ -4387,7 +4387,7 @@ ZenCacheDiskLayer::Flush()
 		WorkerThreadPool& Pool = GetMediumWorkerPool(EWorkloadType::Burst);
 		std::atomic<bool> AbortFlag;
 		std::atomic<bool> PauseFlag;
-		ParallelWork	  Work(AbortFlag, PauseFlag);
+		ParallelWork	  Work(AbortFlag, PauseFlag, WorkerThreadPool::EMode::DisableBacklog);
 		try
 		{
 			for (auto& Bucket : Buckets)
@@ -4434,7 +4434,8 @@ ZenCacheDiskLayer::Scrub(ScrubContext& Ctx)
 		{
 #	if 1
 			Results.push_back(Ctx.ThreadPool().EnqueueTask(
-				std::packaged_task<void()>{[this, Bucket = Kv.second.get(), &Ctx] { Bucket->ScrubStorage(Ctx); }}));
+				std::packaged_task<void()>{[this, Bucket = Kv.second.get(), &Ctx] { Bucket->ScrubStorage(Ctx); }},
+				WorkerThreadPool::EMode::EnableBacklog));
 #	else
 			CacheBucket& Bucket = *Kv.second;
 			Bucket.ScrubStorage(Ctx);