Expose ThreadPool_UnfairSemaphoreSpinLimit config

Spin-wait in ThreadpoolMgr::UnfairSemaphore::Wait can cause significant
CPU usage, which is unnecessary in some scenarios, where threadpool
receives work in bursts. Use of the above parameter will allow fine tuning
of the threadpool behavior based on the workload expectation.

Fix #5928

1 files changed, 2 insertions, 1 deletions

diff --git a/src/vm/win32threadpool.cpp b/src/vm/win32threadpool.cpp
index 35c2b64ac4..95fa5c0ca5 100644
--- a/src/vm/win32threadpool.cpp
+++ b/src/vm/win32threadpool.cpp
@@ -359,7 +359,8 @@ BOOL ThreadpoolMgr::Initialize()
         RetiredCPWakeupEvent->CreateAutoEvent(FALSE);
         _ASSERTE(RetiredCPWakeupEvent->IsValid());
 
-        WorkerSemaphore = new UnfairSemaphore(ThreadCounter::MaxPossibleCount);
+        int spinLimitPerProcessor = CLRConfig::GetConfigValue(CLRConfig::INTERNAL_ThreadPool_UnfairSemaphoreSpinLimit);
+        WorkerSemaphore = new UnfairSemaphore(ThreadCounter::MaxPossibleCount, spinLimitPerProcessor);
 
         RetiredWorkerSemaphore = new CLRSemaphore();
         RetiredWorkerSemaphore->Create(0, ThreadCounter::MaxPossibleCount);