SERVER-52820 Reintroduce yields before waiting for data

1 files changed, 13 insertions, 0 deletions

diff --git a/src/mongo/transport/service_executor.cpp b/src/mongo/transport/service_executor.cpp
index 0a8815bdd22..18efe4c1013 100644
--- a/src/mongo/transport/service_executor.cpp
+++ b/src/mongo/transport/service_executor.cpp
@@ -40,6 +40,7 @@
 #include "mongo/transport/service_executor_fixed.h"
 #include "mongo/transport/service_executor_reserved.h"
 #include "mongo/transport/service_executor_synchronous.h"
+#include "mongo/util/processinfo.h"
 #include "mongo/util/synchronized_value.h"
 
 namespace mongo {
@@ -253,5 +254,17 @@ ServiceExecutor* ServiceExecutorContext::getServiceExecutor() noexcept {
     return transport::ServiceExecutorSynchronous::get(_client->getServiceContext());
 }
 
+void ServiceExecutor::yieldIfAppropriate() const {
+    /*
+     * In perf testing we found that yielding after running a each request produced
+     * at 5% performance boost in microbenchmarks if the number of worker threads
+     * was greater than the number of available cores.
+     */
+    static const auto cores = ProcessInfo::getNumAvailableCores();
+    if (getRunningThreads() > cores) {
+        stdx::this_thread::yield();
+    }
+}
+
 }  // namespace transport
 }  // namespace mongo