Merge pull request #12353 from kpayson64/scatter_read

Use all read buffers when doing a scatter read

src/core/lib/iomgr/tcp_posix.c

@@ -67,7 +67,6 @@ typedef struct {
   grpc_fd *em_fd;
   int fd;
   bool finished_edge;
-  msg_iovlen_type iov_size; /* Number of slices to allocate per read attempt */
   double target_length;
   double bytes_read_this_round;
   gpr_refcount refcount;
@@ -240,7 +239,6 @@ static void tcp_do_read(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
   size_t i;
 
   GPR_ASSERT(!tcp->finished_edge);
-  GPR_ASSERT(tcp->iov_size <= MAX_READ_IOVEC);
   GPR_ASSERT(tcp->incoming_buffer->count <= MAX_READ_IOVEC);
   GPR_TIMER_BEGIN("tcp_continue_read", 0);
 
@@ -252,7 +250,7 @@ static void tcp_do_read(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
   msg.msg_name = NULL;
   msg.msg_namelen = 0;
   msg.msg_iov = iov;
-  msg.msg_iovlen = tcp->iov_size;
+  msg.msg_iovlen = (msg_iovlen_type)tcp->incoming_buffer->count;
   msg.msg_control = NULL;
   msg.msg_controllen = 0;
   msg.msg_flags = 0;
@@ -621,7 +619,6 @@ grpc_endpoint *grpc_tcp_create(grpc_exec_ctx *exec_ctx, grpc_fd *em_fd,
   tcp->min_read_chunk_size = tcp_min_read_chunk_size;
   tcp->max_read_chunk_size = tcp_max_read_chunk_size;
   tcp->bytes_read_this_round = 0;
-  tcp->iov_size = 1;
   tcp->finished_edge = true;
   /* paired with unref in grpc_tcp_destroy */
   gpr_ref_init(&tcp->refcount, 1);