Vote the OS off your Core

Recent trends in OS research have shown evidence that there are performance benefits to running OS services on different cores than the user applications that rely on them. We quantitatively evaluate this claim in terms of one of the most significant architectural constraints: memory performance. To this end, we have created CachEMU, an open-source memory trace generator and cache simulator built as an extension to QEMU for working with system traces. Using CachEMU, we determined that for five common Linux test workloads, it was best to run the OS close, but not too close on the same package, but not on the same core

Analysis of Costs of Production and Profitability for Irrigated Cotton under Smallholder Production Systems; the Case of Middle Awash Valley

አህፅሮትቀጣይነት ያለዉ የግብዓት ዋጋ ጭማሪና የጥጥ ምርት ዋጋ መዋዠቅ በአነስተኛ አምራቾች ዘንድ የጥጥ ምርትን ትርፋማነትና ዘለቄታዊነት ጥያቄ ዉስጥ እንዲወድቅ አድርጎታል፡፡ ይህ ጥናት በአነስተኛ አምራቾች ዘንድ በመስኖ ጥጥን ለማምረት የሚከናወኑ ተግባራትን ከትርፍ አንጻር ለመገምገም በመካከለኛዉ አዋሽ አሚባራ ወረዳ የተከናወነ ነበር፡፡ ጥናቱ 30 የሚሆኑ አነስተኛ የመስኖ ጥጥ አምራቾችን በአላማዊ ናሙና በመምረጥ የተካሄደ ሲሆን የመስኖ ጥጥ ምርት ወጪና ትርፍን ለመለካት የሚያስችሉ ገላጭና የበጀት ቴክኒኮችን ለትንተና ተጠቅሟል፡፡ በተመሳሳይ ትርፍም ኪሳራም የሌለበትን የዋጋና የምርት መጠን እንዲሁም ሊያጋጥሙ የሚችሉ ለዉጦችንና ስጋቶችን ግምት ዉስጥ በማስገባት ትንተና ተካሂዷል፡፡ ዉጤቱም እንደሚያሳየዉ የመስኖ ጥጥን ለማምረት ከሚወጡት ወጪዎች መካከል የሰዉ ጉልበት፤የኬሚካልና የማሽነሪ ወጪዎች ዋናዎቹ ሲሆኑ የባጀት ትንተናዉ ዉጤትም ጥጥ ማምረት በአነስተኛ አምራቾች ደረጃ ትርፋማ እንደሆነ አመላክቷል፡፡ በአነስተኛ አምራቾች ዘንድ ጥጥን በመስኖ ለማምረት የሚያስፈልገዉ የስራ ማስኬጃ ወጪ 20,572.17 ብር በሄክታር የነበረ ሲሆን በተመሳሳይ የተገኘዉ ትርፍ በሄክታር 10,294.23 ብር ነበር፡፡ በተጨማሪም የጥቅም-ወጪ ንጽጽር 1.49 ነበር፡፡ ትርፍ-ኪሳራ አልባ ዋጋና የምርት መጠን ደግሞ 8.35 ብር በ ኪ.ግ እና 1641.83 ኪ.ግ በሄክታር በቅድመ-ተከተል ነበር፡፡ ከዚህ በተጨማሪም ጥናቱ ከመስኖ ጥጥ የሚገኝ ትርፍ ከስራ ማስኬጃ ወጪዎች ይልቅ በምርትና በምርት ዋጋ መቀያየር የበለጠ የሚጠቃ መሆኑን አሳይቷል፡፡ ስለሆነም የጥጥን ትርፋማነትና ምርታማነት ይበልጥ ለማስቀጠል የምርት ዋጋን ማረጋጋትና ምርትን ሊያሳድጉ የሚያስችሉ ግብዓቶችን በተመጣጣኝ ዋጋ ማቅረብ እንደሚገባ ጥናቱ ያመለከተ ሲሆን የተሳለጠ የግብዓትና ምርት ግብይት ይኖር ዘንድ ማህበራትን ማደራጀት ያስፈልጋል፡፡      AbstractThe continuous increase of input costs and volatility of output prices have made the profitability and sustainability of smallholder cotton production in question. This study was carried out to examine the profitability of irrigated cotton production at Amibara district in the Middle Awash Valley under smallholder producers. 30 producers were purposively selected from the villages considered based on the predominance of irrigated cotton production. Primary data were collected for this study using well-structured questionnaires. Data were analyzed using descriptive statistics and budgetary technique analysis. Likewise, break-even and sensitivity analyses were introduced to determine the break-even price and yield and to account to any changes and risks envisaged. The break-up of production cost structure showed that operational (both manual and machinery) expenses were the prominent components of all variable costs. The principal findings of the enterprise budget analysis was that smallholder irrigated cotton production was a profitable enterprise with a gross margin of 10,294.23 Birr per hectare and a total expenditure of 20,572.17 Birr per hectare. Moreover, the benefit cost ratio of 1.49 was obtained. The break-even price and break-even yield at which the producers are at no loss no profit were 8.35 Birr per kg and 1641.83 kg per hectare. Returns from irrigated cotton were highly sensitive to fluctuations of price and yield than total variable cost. Thus, efforts should be made to improve productivity through provision of appropriate agricultural inputs at the lowest possible cost and reduce price volatility by promoting primary cooperatives at district level working on input output marketing

SplitFS: Reducing Software Overhead in File Systems for Persistent Memory

We present SplitFS, a file system for persistent memory (PM) that reduces software overhead significantly compared to state-of-the-art PM file systems. SplitFS presents a novel split of responsibilities between a user-space library file system and an existing kernel PM file system. The user-space library file system handles data operations by intercepting POSIX calls, memory-mapping the underlying file, and serving the read and overwrites using processor loads and stores. Metadata operations are handled by the kernel PM file system (ext4 DAX). SplitFS introduces a new primitive termed relink to efficiently support file appends and atomic data operations. SplitFS provides three consistency modes, which different applications can choose from, without interfering with each other. SplitFS reduces software overhead by up-to 4x compared to the NOVA PM file system, and 17x compared to ext4-DAX. On a number of micro-benchmarks and applications such as the LevelDB key-value store running the YCSB benchmark, SplitFS increases application performance by up to 2x compared to ext4 DAX and NOVA while providing similar consistency guarantees

A Unified Operating System for Clouds and Manycore: fos

Single chip processors with thousands of cores will be available in the next ten years and clouds of multicore processors afford the operating system designer thousands of cores today. Constructing operating systems for manycore and cloud systems face similar challenges. This work identifies these shared challenges and introduces our solution: a factored operating system (fos) designed to meet the scalability, faultiness, variability of demand, and programming challenges of OSâ s for single-chip thousand-core manycore systems as well as current day cloud computers. Current monolithic operating systems are not well suited for manycores and clouds as they have taken an evolutionary approach to scaling such as adding fine grain locks and redesigning subsystems, however these approaches do not increase scalability quickly enough. fos addresses the OS scalability challenge by using a message passing design and is composed out of a collection of Internet inspired servers. Each operating system service is factored into a set of communicating servers which in aggregate implement a system service. These servers are designed much in the way that distributed Internet services are designed, but provide traditional kernel services instead of Internet services. Also, fos embraces the elasticity of cloud and manycore platforms by adapting resource utilization to match demand. fos facilitates writing applications across the cloud by providing a single system image across both future 1000+ core manycores and current day Infrastructure as a Service cloud computers. In contrast, current cloud environments do not provide a single system image and introduce complexity for the user by requiring different programming models for intra- vs inter-machine communication, and by requiring the use of non-OS standard management tools

Fleets: Scalable Services in a Factored Operating System

Current monolithic operating systems are designed for uniprocessor systems, and their architecture reflects this. The rise of multicore and cloud computing is drastically changing the tradeoffs in operating system design. The culture of scarce computational resources is being replaced with one of abundant cores, where spatial layout of processes supplants time multiplexing as the primary scheduling concern. Efforts to parallelize monolithic kernels have been difficult and only marginally successful, and new approaches are needed. This paper presents fleets, a novel way of constructing scalable OS services. With fleets, traditional OS services are factored out of the kernel and moved into user space, where they are further parallelized into a distributed set of concurrent, message-passing servers. We evaluate fleets within fos, a new factored operating system designed from the ground up with scalability as the first-order design constraint. This paper details the main design principles of fleets, and how the system architecture of fos enables their construction. We describe the design and implementation of three critical fleets (network stack, page allocation, and file system) and compare with Linux. These comparisons show that fos achieves superior performance and has better scalability than Linux for large multicores; at 32 cores, fos's page allocator performs 4.5 times better than Linux, and fos's network stack performs 2.5 times better. Additionally, we demonstrate how fleets can adapt to changing resource demand, and the importance of spatial scheduling for good performance in multicores

Using SMT to accelerate nested virtualization

IaaS datacenters offer virtual machines (VMs) to their clients, who in turn sometimes deploy their own virtualized environments, thereby running a VM inside a VM. This is known as nested virtualization. VMs are intrinsically slower than bare-metal execution, as they often trap into their hypervisor to perform tasks like operating virtual I/O devices. Each VM trap requires loading and storing dozens of registers to switch between the VM and hypervisor contexts, thereby incurring costly runtime overheads. Nested virtualization further magnifies these overheads, as every VM trap in a traditional virtualized environment triggers at least twice as many traps. We propose to leverage the replicated thread execution resources in simultaneous multithreaded (SMT) cores to alleviate the overheads of VM traps in nested virtualization. Our proposed architecture introduces a simple mechanism to colocate different VMs and hypervisors on separate hardware threads of a core, and replaces the costly context switches of VM traps with simple thread stall and resume events. More concretely, as each thread in an SMT core has its own register set, trapping between VMs and hypervisors does not involve costly context switches, but simply requires the core to fetch instructions from a different hardware thread. Furthermore, our inter-thread communication mechanism allows a hypervisor to directly access and manipulate the registers of its subordinate VMs, given that they both share the same in-core physical register file. A model of our architecture shows up to 2.3× and 2.6× better I/O latency and bandwidth, respectively. We also show a software-only prototype of the system using existing SMT architectures, with up to 1.3× and 1.5× better I/O latency and bandwidth, respectively, and 1.2--2.2× speedups on various real-world applications

IX Open-source version 1.1 - Deployment and Evaluation Guide

This Technical Report provides the deployment and evaluation guide of the IX dataplane operating system, as of its first open-source release on May 27, 2016. To facilitate the reproduction of our results, we include in this report the precise steps needed to install, deploy and configure IX and its workloads. We reproduce all benchmarks previously published in two peer-reviewed publications at OSDI '14 and SoCC '15 using this up-to-date, open-source code base

RPCValet: NI-Driven Tail-Aware Balancing of µs-Scale RPCs

Modern online services come with stringent quality requirements in terms of response time tail latency. Because of their decomposition into fine-grained communicating software layers, a single user request fans out into a plethora of short, μs-scale RPCs, aggravating the need for faster inter-server communication. In reaction to that need, we are witnessing a technological transition characterized by the emergence of hardware-terminated user-level protocols (e.g., InfiniBand/RDMA) and new architectures with fully integrated Network Interfaces (NIs). Such architectures offer a unique opportunity for a new NI-driven approach to balancing RPCs among the cores of manycore server CPUs, yielding major tail latency improvements for μs-scale RPCs. We introduce RPCValet, an NI-driven RPC load-balancing design for architectures with hardware-terminated protocols and integrated NIs, that delivers near-optimal tail latency. RPCValet's RPC dispatch decisions emulate the theoretically optimal single-queue system, without incurring synchronization overheads currently associated with single-queue implementations. Our design improves throughput under tight tail latency goals by up to 1.4x, and reduces tail latency before saturation by up to 4x for RPCs with μs-scale service times, as compared to current systems with hardware support for RPC load distribution. RPCValet performs within 15% of the theoretically optimal single-queue system

Household Possession and Use of Insecticide-Treated Mosquito Nets in Sierra Leone 6 Months after a National Mass-Distribution Campaign

BACKGROUND: In November 2010, Sierra Leone distributed over three million long-lasting insecticide-treated nets (LLINs) with the objective of providing protection from malaria to individuals in all households in the country. METHODS: We conducted a nationally representative survey six months after the mass distribution campaign to evaluate its impact on household insecticide-treated net (ITN) ownership and use. We examined factors associated with household ITN possession and use with logistic regression models. RESULTS: The survey included 4,620 households with equal representation in each of the 14 districts. Six months after the campaign, 87.6% of households own at least one ITN, which represents an increase of 137% over the most recent estimate of 37% in 2008. Thirty-six percent of households possess at least one ITN per two household members; rural households were more likely than urban households to have ≥ 1:2 ITN to household members, but there was no difference by socio-economic status or household head education. Among individuals in households possessing ≥ 1 ITN, 76.5% slept under an ITN the night preceding the survey. Individuals in households where the household head had heard malaria messaging, had correct knowledge of malaria transmission, and where at least one ITN was hanging, were more likely to have slept under an ITN. CONCLUSIONS: The mass distribution campaign was effective at achieving high coverage levels across the population, notably so among rural households where the malaria burden is higher. These important gains in equitable access to malaria prevention will need to be maintained to produce long-term reductions in the malaria burden