Add support for readv functions

Summary: Add support for readv functions

Reviewed By: mingtaoy

Differential Revision: D40089998

fbshipit-source-id: 577a8f6c2bd1b833544ff7ce6400b4d3a9dc222f

fizz/protocol/AsyncFizzBase.cpp

@@ -33,9 +33,7 @@ AsyncFizzBase::AsyncFizzBase(
     : folly::WriteChainAsyncTransportWrapper<folly::AsyncTransportWrapper>(
           std::move(transport)),
       handshakeTimeout_(*this, transport_->getEventBase()),
-      transportOptions_(std::move(options)),
-      ioVecQueue_(folly::IOBufIovecBuilder::Options().setBlockSize(
-          transportOptions_.readVecBlockSize)) {
+      transportOptions_(std::move(options)) {
   setReadMode(transportOptions_.readMode);
 }
 
@@ -413,14 +411,16 @@ void AsyncFizzBase::getReadBuffer(void** bufReturn, size_t* lenReturn) {
 }
 
 void AsyncFizzBase::getReadBuffers(folly::IOBufIovecBuilder::IoVecVec& iovs) {
-  ioVecQueue_.allocateBuffers(iovs, transportOptions_.readVecReadSize);
+  DCHECK(!!transportOptions_.ioVecQueue);
+  transportOptions_.ioVecQueue->allocateBuffers(iovs);
 }
 
 void AsyncFizzBase::readDataAvailable(size_t len) noexcept {
   DelayedDestruction::DestructorGuard dg(this);
 
   if (getReadMode() == folly::AsyncTransport::ReadCallback::ReadMode::ReadVec) {
-    auto tmp = ioVecQueue_.extractIOBufChain(len);
+    DCHECK(!!transportOptions_.ioVecQueue);
+    auto tmp = transportOptions_.ioVecQueue->extractIOBufChain(len);
     transportReadBuf_.append(std::move(tmp));
   } else {
     transportReadBuf_.postallocate(len);

fizz/protocol/AsyncFizzBase.h

@@ -84,6 +84,14 @@ class AsyncFizzBase : public folly::WriteChainAsyncTransportWrapper<
         std::unique_ptr<folly::IOBuf> endOfData) = 0;
   };
 
+  /* Interface used to get a reference to an folly::IOBufIovecBuilder
+   */
+  struct IOVecQueueOps {
+    virtual ~IOVecQueueOps() = default;
+    virtual void allocateBuffers(folly::IOBufIovecBuilder::IoVecVec& iovs) = 0;
+    virtual std::unique_ptr<folly::IOBuf> extractIOBufChain(size_t len) = 0;
+  };
+
   struct TransportOptions {
     /**
      * Controls whether or not the async recv callback should be registered
@@ -106,22 +114,23 @@ class AsyncFizzBase : public folly::WriteChainAsyncTransportWrapper<
      *   ReadMode::ReadVec
      *      Under this mode, Fizz will use vectored IO (`readv`) to read
      *      incoming data. This can help avoid additional copies at the expense
-     *      of allocating extra ref counting objects. The overall mem usage is
-     * also dependent on the readVecBlockSize value.
+     *      of allocating extra ref counting objects.
      *
      */
     folly::AsyncReader::ReadCallback::ReadMode readMode{ReadMode::ReadBuffer};
 
     /*
-     * AsyncTransport read vec block size
-     */
-    size_t readVecBlockSize{
-        folly::IOBufIovecBuilder::Options::kDefaultBlockSize};
-
-    /*
-     * AsyncTransport read vec read size
+     * Under `ReadMode::ReadVec`, Fizz will allocate buffers for vectored I/O
+     * through the `iovecQueue`.
+     *
+     * This field must be set if `readMode` is `ReadMode::ReadVec`.
+     *
+     * Multiple AsyncFizzBase instances may share the underlying
+     * `IOVecQueueOps`, provided that the implementation allows it. This can be
+     * useful in limiting the amount of memory allocated across a process with
+     * many Fizz connections.
      */
-    size_t readVecReadSize{4000};
+    std::shared_ptr<IOVecQueueOps> ioVecQueue{};
 
     /**
      * Under ReadMode::ReadBuffer, whenever Fizz's available read buffer space
@@ -519,7 +528,5 @@ class AsyncFizzBase : public folly::WriteChainAsyncTransportWrapper<
 
   TransportOptions transportOptions_;
   std::unique_ptr<FizzMsgHdr> msgHdr_;
-
-  folly::IOBufIovecBuilder ioVecQueue_;
 };
 } // namespace fizz

fizz/test/AsyncFizzBaseTest.cpp

@@ -270,15 +270,19 @@ MATCHER_P(BufMatches, expected, "") {
 }
 
 struct ReadCB {
-  constexpr static AsyncFizzBase::TransportOptions Options = {
-      false, // registerEventCallback
-  };
+  static const AsyncFizzBase::TransportOptions Options;
+};
+
+const AsyncFizzBase::TransportOptions ReadCB::Options = {
+    false, // registerEventCallback
 };
 
 struct RecvCB {
-  constexpr static AsyncFizzBase::TransportOptions Options = {
-      true, // registerEventCallback
-  };
+  static const AsyncFizzBase::TransportOptions Options;
+};
+
+const AsyncFizzBase::TransportOptions RecvCB::Options = {
+    true, // registerEventCallback
 };
 
 using TestTypes = ::testing::Types<ReadCB, RecvCB>;