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MemoryExpansion Technology (MXT): Software support and performance A novel memory subsystem called Memory Expansion Technology (MXT) has been built for fast hardware compression of main-memory content. This allows a memory expansion to present a "real" memory larger than the physically available memory. This paper provides an overview of the memorycompression architecture, its OS support under Linux and Windows ® , and an analysis of the performance impact of memory compression. Results show that the hardware compression of main memory has a negligible penalty compared to an uncompressed main memory, and for memory-starved applications it increases performance significantly. We also show that the memory content of an application can usually be compressed by a factor of 2.

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Keywords:Big data platforms, Composable system architecture, Disaggregated datacenter architecture, composable datacenter, software defined environments, software defined networking. Abstract:The rapid growth of cloud computing, both in terms of the spectrum and volume of cloud workloads, necessitate re-visiting the traditional rack-mountable servers based datacenter design. Next generation datacenters need to offer enhanced support for: (i) fast changing system configuration requirements due to workload constraints, (ii) timely adoption of emerging hardware technologies, and (iii) maximal sharing of systems and subsystems in order to lower costs. Disaggregated datacenters, constructed as a collection of individual resources such as CPU, memory, disks etc., and composed into workload execution units on demand, are an interesting new trend that can address the above challenges. In this paper, we demonstrated the feasibility of composable systems through building a rack scale composable system prototype using PCIe switch. Through empirical approaches, we develop assessment of the opportunities and challenges for leveraging the composable architecture for rack scale cloud datacenters with a focus on big data and NoSQL workloads. In particular, we compare and contrast the programming models that can be used to access the composable resources, and developed the implications for the network and resource provisioning and management for rack scale architecture.

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Recently, high speed interconnects capable of remote direct memory access (RDMA) such as InfiniBand and iWARP have gained considerable popularity due to their superb latency and bandwidth. Most existing studies about RDMA focus on its performance aspect. However, as power management has become essential for high-end systems such as enterprise servers and high performance computing nodes which are often equipped with RDMA capable network adapters, it is very important for us to take a fresh look at the benefits of RDMA from the power perspective.In the paper, we provide a detailed empirical study of the benefits of RDMA in terms of power savings compared with traditional communication protocols such as TCP/IP. We used two popular RDMA adapters in our evaluations: Mellanox ConnectX InfiniBand HCAs and Chelsio T3 10GE RNICs. In order to isolate the impact of communication on power consumption, our evaluation focused on using microbenchmarks which perform different communication patterns. We have also studied several important factors that may have an impact on the performance and the power consumption of RDMA adapters such as the use of polling versus blocking, CPU speeds, and extra memory copies.We show that using high speed RDMA adapters can result in significant amount of power consumption during communication. (In one test, the system power has increased by as much as 50 watts, or over 30% of the idle power.) We found that RDMA generally has better power efficiency compared to that of TCP/IP, especially for communication intensive phases, for example when large messages are transferred. The power savings of RDMA are achieved by minimizing the interactions between the network adapters and other system components such as the CPUs and the memory: Although nearly the same amount of data must be going through the network adapters for both RDMA and TCP/IP, RDMA rePermission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. quires much fewer CPU cycles for protocol processing and also generates less memory bus traffic, both of which contribute to its power savings.Overall, our research demonstrated that RDMA not only provides high communication performance, but also offers excellent power efficiency, making it a desirable choice in environments that have strict power/energy constraints and demand high communication performance.

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