http2: allocate on every chunk send

Previously, we were using a shared stack allocated buffer to hold the serialized outbound data but that runs into issues if the outgoing stream does not write or copy immediately. Instead, allocate a buffer each time. Slight additional overhead here, but necessary. Later on, once we've analyzed this more, we might be able to switch to a stack allocated ring or slab buffer but that's a bit more complicated than what we strictly need right now.
jasnell · Nov 1, 2017 · Nov 2, 2017 · Nov 2, 2017 · 125e1b5c0dd9891479c5c9e79823f4e43bf8bce5 · apapirovski
commit 125e1b5c0dd9891479c5c9e79823f4e43bf8bce5
diff --git a/src/node_http2.cc b/src/node_http2.cc
@@ -893,32 +893,33 @@ int Http2Session::DoWrite(WriteWrap* req_wrap,
   return 0;
 }
 
-void Http2Session::AllocateSend(uv_buf_t* buf) {
-  buf->base = stream_alloc();
-  buf->len = kAllocBufferSize;
+size_t Http2Session::AllocateSend(WriteWrap** req) {
+  HandleScope scope(env()->isolate());
+  auto AfterWrite = [](WriteWrap* req, int status) {
+    req->Dispose();
+  };
+  Local<Object> obj =
+      env()->write_wrap_constructor_function()
+          ->NewInstance(env()->context()).ToLocalChecked();
+  // Base the amount allocated on the remote peers max frame size
+  uint32_t size =
+      nghttp2_session_get_remote_settings(
+          session(),
+          NGHTTP2_SETTINGS_MAX_FRAME_SIZE);
+  *req = WriteWrap::New(env(), obj, this, AfterWrite, size);
+  return size;
 }
 
-void Http2Session::Send(uv_buf_t* buf, size_t length) {
+void Http2Session::Send(WriteWrap* req, char* buf, size_t length) {
   DEBUG_HTTP2("Http2Session: Attempting to send data\n");
   if (stream_ == nullptr || !stream_->IsAlive() || stream_->IsClosing()) {
     return;
   }
-  HandleScope scope(env()->isolate());
-  auto AfterWrite = [](WriteWrap* req_wrap, int status) {
-    req_wrap->Dispose();
-  };
-  Local<Object> req_wrap_obj =
-      env()->write_wrap_constructor_function()
-          ->NewInstance(env()->context()).ToLocalChecked();
-  WriteWrap* write_req = WriteWrap::New(env(),
-                                        req_wrap_obj,
-                                        this,
-                                        AfterWrite);
 
   chunks_sent_since_last_write_++;
-  uv_buf_t actual = uv_buf_init(buf->base, length);
-  if (stream_->DoWrite(write_req, &actual, 1, nullptr)) {
-    write_req->Dispose();
+  uv_buf_t actual = uv_buf_init(buf, length);
+  if (stream_->DoWrite(req, &actual, 1, nullptr)) {
+    req->Dispose();
   }
 }
 

diff --git a/src/node_http2.h b/src/node_http2.h
@@ -384,7 +384,6 @@ class Http2Session : public AsyncWrap,
       nghttp2_headers_category cat,
       uint8_t flags) override;
   void OnStreamClose(int32_t id, uint32_t code) override;
-  void Send(uv_buf_t* bufs, size_t total) override;
   void OnDataChunk(Nghttp2Stream* stream, uv_buf_t* chunk) override;
   void OnSettings(bool ack) override;
   void OnPriority(int32_t stream,
@@ -398,7 +397,9 @@ class Http2Session : public AsyncWrap,
   void OnFrameError(int32_t id, uint8_t type, int error_code) override;
   void OnTrailers(Nghttp2Stream* stream,
                   const SubmitTrailers& submit_trailers) override;
-  void AllocateSend(uv_buf_t* buf) override;
+
+  void Send(WriteWrap* req, char* buf, size_t length) override;
+  size_t AllocateSend(WriteWrap** req);
 
   int DoWrite(WriteWrap* w, uv_buf_t* bufs, size_t count,
               uv_stream_t* send_handle) override;

diff --git a/src/node_http2_core-inl.h b/src/node_http2_core-inl.h
@@ -490,17 +490,21 @@ inline void Nghttp2Session::SendPendingData() {
   if (IsDestroying())
     return;
 
-  uv_buf_t dest;
-  AllocateSend(&dest);
+  WriteWrap* req = nullptr;
+  char* dest = nullptr;
+  size_t destRemaining = 0;
   size_t destLength = 0;             // amount of data stored in dest
-  size_t destRemaining = dest.len;   // amount space remaining in dest
   size_t destOffset = 0;             // current write offset of dest
 
   const uint8_t* src;                // pointer to the serialized data
   ssize_t srcLength = 0;             // length of serialized data chunk
 
   // While srcLength is greater than zero
   while ((srcLength = nghttp2_session_mem_send(session_, &src)) > 0) {
+    if (req == nullptr) {
+      destRemaining = AllocateSend(&req);
+      dest = req->Extra();
+    }
     DEBUG_HTTP2("Nghttp2Session %s: nghttp2 has %d bytes to send\n",
                 TypeName(), srcLength);
     size_t srcRemaining = srcLength;
@@ -512,18 +516,19 @@ inline void Nghttp2Session::SendPendingData() {
     while (srcRemaining > destRemaining) {
       DEBUG_HTTP2("Nghttp2Session %s: pushing %d bytes to the socket\n",
                   TypeName(), destLength + destRemaining);
-      memcpy(dest.base + destOffset, src + srcOffset, destRemaining);
+      memcpy(dest + destOffset, src + srcOffset, destRemaining);
       destLength += destRemaining;
-      Send(&dest, destLength);
+      Send(req, dest, destLength);
       destOffset = 0;
       destLength = 0;
       srcRemaining -= destRemaining;
       srcOffset += destRemaining;
-      destRemaining = dest.len;
+      destRemaining = AllocateSend(&req);
+      dest = req->Extra();
     }
 
     if (srcRemaining > 0) {
-      memcpy(dest.base + destOffset, src + srcOffset, srcRemaining);
+      memcpy(dest + destOffset, src + srcOffset, srcRemaining);
       destLength += srcRemaining;
       destOffset += srcRemaining;
       destRemaining -= srcRemaining;
@@ -535,7 +540,7 @@ inline void Nghttp2Session::SendPendingData() {
   if (destLength > 0) {
     DEBUG_HTTP2("Nghttp2Session %s: pushing %d bytes to the socket\n",
                 TypeName(), destLength);
-    Send(&dest, destLength);
+    Send(req, dest, destLength);
   }
 }
 

diff --git a/src/node_http2_core.h b/src/node_http2_core.h
@@ -3,6 +3,7 @@
 
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
+#include "stream_base.h"
 #include "util-inl.h"
 #include "uv.h"
 #include "nghttp2/nghttp2.h"
@@ -153,7 +154,6 @@ class Nghttp2Session {
   // Removes a stream instance from this session
   inline void RemoveStream(int32_t id);
 
-  virtual void Send(uv_buf_t* buf, size_t length) {}
   virtual void OnHeaders(
       Nghttp2Stream* stream,
       std::queue<nghttp2_header>* headers,
@@ -176,7 +176,10 @@ class Nghttp2Session {
                             int error_code) {}
   virtual ssize_t GetPadding(size_t frameLength,
                              size_t maxFrameLength) { return 0; }
-  virtual void AllocateSend(uv_buf_t* buf) = 0;
+
+  inline void SendPendingData();
+  virtual void Send(WriteWrap* req, char* buf, size_t length) = 0;
+  virtual size_t AllocateSend(WriteWrap** req) = 0;
 
   virtual bool HasGetPaddingCallback() { return false; }
 
@@ -199,8 +202,6 @@ class Nghttp2Session {
   virtual void OnTrailers(Nghttp2Stream* stream,
                           const SubmitTrailers& submit_trailers) {}
 
-  inline void SendPendingData();
-
   virtual uv_loop_t* event_loop() const = 0;
 
   virtual void Close();