Latency (engineering)

About: Latency (engineering) is a research topic. Over the lifetime, 7278 publications have been published within this topic receiving 115409 citations. The topic is also known as: lag.

BubbleUp: low latency fast-scan for media servers

Abstract: Interactive multimedia applications require fast response time. Traditional disk scheduling schemes can incur high latencies, and caching data in memory to reduce latency is usually not feasible, especially if fast-scans need to be supported. In this study we propose a disk-based solution called BubbleUp. It significantly reduces the initial latency for new requests, as well as for fast-scan requests. The throughput of the scheme is comparable to that of traditional schemes, and it may even provide better throughput than mechanisms based on elevator disk scheduling. BubbleUp incurs a slight disk storage overhead, but we argue that through effective allocation, this cost can be minimized.

DX: Latency-Based Congestion Control for Datacenters

Abstract: Since the advent of datacenter networking, achieving low latency within the network has been a primary goal. Many congestion control schemes have been proposed in recent years to meet the datacenters’ unique performance requirement. The nature of congestion feedback largely governs the behavior of congestion control. In datacenter networks, where round trip times are in hundreds of microseconds, accurate feedback is crucial to achieve both high utilization and low queueing delay. Proposals for datacenter congestion control predominantly leverage explicit congestion notification (ECN) or even explicit in-network feedback to minimize the queuing delay. In this paper, we explore latency-based feedback as an alternative and show its advantages over ECN. Against the common belief that such implicit feedback is noisy and inaccurate, we demonstrate that latency-based implicit feedback is accurate enough to signal a single packet’s queuing delay in 10 Gb/s networks. Such high accuracy enables us to design a new congestion control algorithm, DX, that performs fine-grained control to adjust the congestion window just enough to achieve very low queuing delay while attaining full utilization. Our extensive evaluation shows that: 1) the latency measurement accurately reflects the one-way queuing delay in single packet level; 2) the latency feedback can be used to perform practical and fine-grained congestion control in high-speed datacenter networks; and 3) DX outperforms DCTCP with 5.33 times smaller median queueing delay at 1 Gb/s and 1.57 times at 10 Gb/s.

Network interface design for low latency request-response protocols

Abstract: Ethernet network interfaces in commodity systems are designed with a focus on achieving high bandwidth at low CPU utilization, while often sacrificing latency. This approach is viable only if the high interface latency is still overwhelmingly dominated by software request processing times. However, recent efforts to lower software latency in request-response based systems, such as memcached and RAMCloud, have promoted network interface into a significant contributor to the overall latency. We present a low latency network interface design suitable for request-response based applications. Evaluation on a prototype FPGA implementation has demonstrated that our design exhibits more than double latency improvements without a meaningful negative impact on either bandwidth or CPU power. We also investigate latency-power tradeoffs between using interrupts and polling, as well as the effects of processor's low power states.