Add option to do an inline write after a read event.

Summary: Presently updateWriteLooper will always schedule a loop callback to do the write loop. Add an option to inline trigger the writes after the read event.

Reviewed By: kvtsoy, sharmafb

Differential Revision: D62192192

fbshipit-source-id: 30991608f57fbfa097a7522c0731d25b8e528345

quic/api/QuicTransportBase.cpp

@@ -1114,7 +1114,7 @@ void QuicTransportBase::updatePeekLooper() {
   }
 }
 
-void QuicTransportBase::updateWriteLooper(bool thisIteration) {
+void QuicTransportBase::updateWriteLooper(bool thisIteration, bool runInline) {
   if (closeState_ == CloseState::CLOSED) {
     VLOG(10) << nodeToString(conn_->nodeType)
              << " stopping write looper because conn closed " << *this;
@@ -1141,7 +1141,7 @@ void QuicTransportBase::updateWriteLooper(bool thisIteration) {
     VLOG(10) << nodeToString(conn_->nodeType)
              << " running write looper thisIteration=" << thisIteration << " "
              << *this;
-    writeLooper_->run(thisIteration);
+    writeLooper_->run(thisIteration, runInline);
     if (conn_->loopDetectorCallback) {
       conn_->writeDebugState.needsWriteLoopDetect =
           (conn_->loopDetectorCallback != nullptr);
@@ -1878,7 +1878,7 @@ void QuicTransportBase::onNetworkData(
     checkForClosedStream();
     updateReadLooper();
     updatePeekLooper();
-    updateWriteLooper(true);
+    updateWriteLooper(true, conn_->transportSettings.inlineWriteAfterRead);
   };
   try {
     conn_->lossState.totalBytesRecvd += networkData.getTotalData();

quic/api/QuicTransportBase.h

@@ -705,7 +705,7 @@ class QuicTransportBase : public QuicSocket,
   void invokeStreamsAvailableCallbacks();
   void updateReadLooper();
   void updatePeekLooper();
-  void updateWriteLooper(bool thisIteration);
+  void updateWriteLooper(bool thisIteration, bool runInline = false);
   void handlePingCallbacks();
   void handleKnobCallbacks();
   void handleAckEventCallbacks();

quic/common/FunctionLooper.cpp

@@ -75,7 +75,7 @@ void FunctionLooper::runLoopCallback() noexcept {
   commonLoopBody();
 }
 
-void FunctionLooper::run(bool thisIteration) noexcept {
+void FunctionLooper::run(bool thisIteration, bool runInline) noexcept {
   VLOG(10) << __func__ << ": " << type_;
   running_ = true;
   // Caller can call run() in func_. But if we are in pacing mode, we should
@@ -85,6 +85,13 @@ void FunctionLooper::run(bool thisIteration) noexcept {
             << " in loop body and using pacing - not rescheduling";
     return;
   }
+  if (runInline) {
+    // Running inline, manually trigger a loop body and cancel the loop
+    // callback if it was scheduled.
+    cancelLoopCallback();
+    commonLoopBody();
+    return;
+  }
   if (isLoopCallbackScheduled() ||
       (!fireLoopEarly_ && pacingTimer_ && isTimerCallbackScheduled())) {
     VLOG(10) << __func__ << ": " << type_ << " already scheduled";

quic/common/FunctionLooper.h

@@ -51,7 +51,7 @@ class FunctionLooper : public QuicEventBaseLoopCallback,
    * Starts running the loop callback in each loop iteration.
    * if this is already scheduled to run, run() will continue to run it.
    */
-  void run(bool thisIteration = false) noexcept;
+  void run(bool thisIteration = false, bool runInline = false) noexcept;
 
   void setPacingFunction(
       folly::Function<std::chrono::microseconds()>&& pacingFunc);

quic/state/TransportSettings.h

@@ -403,6 +403,9 @@ struct TransportSettings {
   bool checkIdleTimerOnWrite{false};
   // Whether to process callbacks per received packet.
   bool processCallbacksPerPacket{false};
+  // Whether to trigger an inline write loop after we've read packets, rather
+  // than deferring to a loop callback.
+  bool inlineWriteAfterRead{false};
 };
 
 } // namespace quic