In this paper, we propose OmniFlow, a novel transport protocol which combines load balancing and flow control at the transport layer to optimize datacenter transfers. OmniFlow outweighs previous solutions in two aspects. Firstly, it can simultaneously and precisely measure the queueing latencies on multiple paths between two hosts. Secondly, OmniFlow adaptively integrates the load balancing and flow control modules and shares the same congestion metrics (i.e. queueing latencies) between them. Based on different network conditions, it either dynamically reroutes flows to utilize the bisection bandwidth or proactively adjusts flow rates to bound queueing occupancies. Our results show that OmniFlow can provide both low latency for small flows without sacrificing the throughput of elephant flows.