transport: Reduce heap allocations

internal/transport/http2_client.go

@@ -500,12 +500,10 @@ func (t *http2Client) newStream(ctx context.Context, callHdr *CallHdr) *ClientSt
 	s.ctx = ctx
 	s.trReader = transportReader{
 		reader: recvBufferReader{
-			ctx:     s.ctx,
-			ctxDone: s.ctx.Done(),
-			recv:    &s.buf,
-			closeStream: func(err error) {
-				s.Close(err)
-			},
+			ctx:          s.ctx,
+			ctxDone:      s.ctx.Done(),
+			recv:         &s.buf,
+			clientStream: s,
 		},
 		windowHandler: s,
 	}

internal/transport/transport.go

@@ -123,13 +123,13 @@ func (b *recvBuffer) get() <-chan recvMsg {
 // recvBufferReader implements io.Reader interface to read the data from
 // recvBuffer.
 type recvBufferReader struct {
-	_           noCopy
-	closeStream func(error) // Closes the client transport stream with the given error and nil trailer metadata.
-	ctx         context.Context
-	ctxDone     <-chan struct{} // cache of ctx.Done() (for performance).
-	recv        *recvBuffer
-	last        mem.Buffer // Stores the remaining data in the previous calls.
-	err         error
+	_            noCopy
+	clientStream *ClientStream // The client transport stream is closed with the given error and nil trailer metadata.
+	ctx          context.Context
+	ctxDone      <-chan struct{} // cache of ctx.Done() (for performance).
+	recv         *recvBuffer
+	last         mem.Buffer // Stores the remaining data in the previous calls.
+	err          error
 }
 
 func (r *recvBufferReader) ReadMessageHeader(header []byte) (n int, err error) {
@@ -140,7 +140,7 @@ func (r *recvBufferReader) ReadMessageHeader(header []byte) (n int, err error) {
 		n, r.last = mem.ReadUnsafe(header, r.last)
 		return n, nil
 	}
-	if r.closeStream != nil {
+	if r.clientStream != nil {
 		n, r.err = r.readMessageHeaderClient(header)
 	} else {
 		n, r.err = r.readMessageHeader(header)
@@ -165,7 +165,7 @@ func (r *recvBufferReader) Read(n int) (buf mem.Buffer, err error) {
 		}
 		return buf, nil
 	}
-	if r.closeStream != nil {
+	if r.clientStream != nil {
 		buf, r.err = r.readClient(n)
 	} else {
 		buf, r.err = r.read(n)
@@ -210,7 +210,7 @@ func (r *recvBufferReader) readMessageHeaderClient(header []byte) (n int, err er
 		// TODO: delaying ctx error seems like a unnecessary side effect. What
 		// we really want is to mark the stream as done, and return ctx error
 		// faster.
-		r.closeStream(ContextErr(r.ctx.Err()))
+		r.clientStream.Close(ContextErr(r.ctx.Err()))
 		m := <-r.recv.get()
 		return r.readMessageHeaderAdditional(m, header)
 	case m := <-r.recv.get():
@@ -237,7 +237,7 @@ func (r *recvBufferReader) readClient(n int) (buf mem.Buffer, err error) {
 		// TODO: delaying ctx error seems like a unnecessary side effect. What
 		// we really want is to mark the stream as done, and return ctx error
 		// faster.
-		r.closeStream(ContextErr(r.ctx.Err()))
+		r.clientStream.Close(ContextErr(r.ctx.Err()))
 		m := <-r.recv.get()
 		return r.readAdditional(m, n)
 	case m := <-r.recv.get():

preloader.go

@@ -47,9 +47,6 @@ func (p *PreparedMsg) Encode(s Stream, msg any) error {
 	}
 
 	// check if the context has the relevant information to prepareMsg
-	if rpcInfo.preloaderInfo == nil {
-		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo is nil")
-	}
 	if rpcInfo.preloaderInfo.codec == nil {
 		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo.codec is nil")
 	}

rpc_util.go

@@ -961,7 +961,7 @@ func recv(p *parser, c baseCodec, s recvCompressor, dc Decompressor, m any, maxR
 // Information about RPC
 type rpcInfo struct {
 	failfast      bool
-	preloaderInfo *compressorInfo
+	preloaderInfo compressorInfo
 }
 
 // Information about Preloader
@@ -980,7 +980,7 @@ type rpcInfoContextKey struct{}
 func newContextWithRPCInfo(ctx context.Context, failfast bool, codec baseCodec, cp Compressor, comp encoding.Compressor) context.Context {
 	return context.WithValue(ctx, rpcInfoContextKey{}, &rpcInfo{
 		failfast: failfast,
-		preloaderInfo: &compressorInfo{
+		preloaderInfo: compressorInfo{
 			codec: codec,
 			cp:    cp,
 			comp:  comp,

stream.go

@@ -177,6 +177,8 @@ func NewClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 	return cc.NewStream(ctx, desc, method, opts...)
 }
 
+var emptyMethodConfig = serviceconfig.MethodConfig{}
+
 func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, opts ...CallOption) (_ ClientStream, err error) {
 	// Start tracking the RPC for idleness purposes. This is where a stream is
 	// created for both streaming and unary RPCs, and hence is a good place to
@@ -217,7 +219,7 @@ func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 		return nil, err
 	}
 
-	var mc serviceconfig.MethodConfig
+	mc := &emptyMethodConfig
 	var onCommit func()
 	newStream := func(ctx context.Context, done func()) (iresolver.ClientStream, error) {
 		return newClientStreamWithParams(ctx, desc, cc, method, mc, onCommit, done, nameResolutionDelayed, opts...)
@@ -240,7 +242,7 @@ func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 		if rpcConfig.Context != nil {
 			ctx = rpcConfig.Context
 		}
-		mc = rpcConfig.MethodConfig
+		mc = &rpcConfig.MethodConfig
 		onCommit = rpcConfig.OnCommitted
 		if rpcConfig.Interceptor != nil {
 			rpcInfo.Context = nil
@@ -258,7 +260,7 @@ func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 	return newStream(ctx, func() {})
 }
 
-func newClientStreamWithParams(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, mc serviceconfig.MethodConfig, onCommit, doneFunc func(), nameResolutionDelayed bool, opts ...CallOption) (_ iresolver.ClientStream, err error) {
+func newClientStreamWithParams(ctx context.Context, desc *StreamDesc, cc *ClientConn, method string, mc *serviceconfig.MethodConfig, onCommit, doneFunc func(), nameResolutionDelayed bool, opts ...CallOption) (_ iresolver.ClientStream, err error) {
 	callInfo := defaultCallInfo()
 	if mc.WaitForReady != nil {
 		callInfo.failFast = !*mc.WaitForReady
@@ -325,7 +327,7 @@ func newClientStreamWithParams(ctx context.Context, desc *StreamDesc, cc *Client
 	cs := &clientStream{
 		callHdr:             callHdr,
 		ctx:                 ctx,
-		methodConfig:        &mc,
+		methodConfig:        mc,
 		opts:                opts,
 		callInfo:            callInfo,
 		cc:                  cc,