Support zero-copy for low-latency combine

csrc/config.hpp

@@ -103,7 +103,7 @@ struct LowLatencyBuffer {
     int* combine_rdma_recv_flag_buffer = nullptr;
 
     void* combine_rdma_send_buffer_data_start = nullptr;
-    int num_bytes_per_combine_msg = 0;
+    size_t num_bytes_per_combine_msg = 0;
 
     std::pair<int*, int> clean_meta() {
         EP_HOST_ASSERT(dispatch_rdma_recv_count_buffer == combine_rdma_recv_flag_buffer);
@@ -168,7 +168,7 @@ struct LowLatencyLayout {
                 advance(rdma_buffer, send_buffer_bytes * 2 + recv_buffer_bytes * i),
                 advance<int*>(rdma_buffer, send_buffer_bytes * 2 + recv_buffer_bytes * 2 + signaling_buffer_bytes * i),
                 advance(rdma_buffer, send_buffer_bytes * i + sizeof(int4)),
-                static_cast<int>(num_bytes_per_combine_msg)
+                num_bytes_per_combine_msg
             };
         }
     }