15821307
The performance analysis of linux networking - Packet receiving
The computing models for high-energy physics experiments are becoming ever more globally distributed and grid-based, both for technical reasons (e.g., to place computational and data resources near each other and the demand) and for strategic reasons (e.g., to leverage equipment investments). To support such computing models, the network and end systems, computing and storage, face unprecedented challenges. One of the biggest challenges is to transfer scientific data sets - now in the multi-petabyte (10^1^5 bytes) range and expected to grow to exabytes within a decade - reliably and efficiently among facilities and computation centers scattered around the world. Both the network and end systems should be able to provide the capabilities to support high bandwidth, sustained, end-to-end data transmission. Recent trends in technology are showing that although the raw transmission speeds used in networks are increasing rapidly, the rate of advancement of microprocessor technology has slowed down. Therefore, network protocol-processing overheads have risen sharply in comparison with the time spent in packet transmission, resulting in degraded throughput for networked applications. More and more, it is the network end system, instead of the network, that is responsible for degraded performance of network applications. In this paper, the Linux system's packet receive process is studied from NIC to application. We develop a mathematical model to characterize the Linux packet receiving process. Key factors that affect Linux systems' network performance are analyzed.
60653560
A collaborative network middleware project by Lambda Station, TeraPaths, and Phoebus
The TeraPaths, Lambda Station, and Phoebus projects, funded by the US Department of Energy, have successfully developed network middleware services that establish on-demand and manage true end-to-end, Quality-of-Service (QoS) aware, virtual network paths across multiple administrative network domains, select network paths and gracefully reroute traffic over these dynamic paths, and streamline traffic between packet and circuit networks using transparent gateways. These services improve network QoS and performance for applications, playing a critical role in the effective use of emerging dynamic circuit network services. They provide interfaces to applications, such as dCache SRM, translate network service requests into network device configurations, and coordinate with each other to setup up end-to-end network paths. The End Site Control Plane Subsystem (ESCPS) builds upon the success of the three projects by combining their individual capabilities into the next generation of network middleware. ESCPS addresses challenges such as cross-domain control plane signalling and interoperability, authentication and authorization in a Grid environment, topology discovery, and dynamic status tracking. The new network middleware will take full advantage of the perfSONAR monitoring infrastructure and the Inter-Domain Control plane efforts and will be deployed and fully vetted in the Large Hadron Collider data movement environment.
11433371
Potential performance bottleneck in Linux TCP
TCP is the most widely used transport protocol on the Internet today. Over the years, especially recently, due to requirements of high bandwidth transmission, various approaches have been proposed to improve TCP performance. The Linux 2.6 kernel is now preemptible. It can be interrupted mid-task, making the system more responsive and interactive. However, we have noticed that Linux kernel preemption can interact badly with the performance of the networking subsystem. In this paper we investigate the performance bottleneck in Linux TCP. We systematically describe the trip of a TCP packet from its ingress into a Linux network end system to its final delivery to the application; we study the performance bottleneck in Linux TCP through mathematical modeling and practical experiments; finally we propose and test one possible solution to resolve this performance bottleneck in Linux TCP.
203169
An evaluation of parallel optimization for OpenSolaris® network stack
Computing is now shifting towards multiprocessing. The fundamental goal of multiprocessing is improved performance through the introduction of additional hardware threads or cores (referred to as “cores” for simplicity). Modern network stacks can exploit parallel cores to allow either message-based parallelism or connection-based parallelism as a means to enhance performance. OpenSolaris has redesigned and parallelized to better utilize additional cores. Three special technologies, named Softring Set, Soft ring and Squeue are introduced in OpenSolaris for stack parallelization. In this paper, we study the OpenSolaris packet receiving process and its core parallelism optimization techniques. Experiment results show that these techniques allow OpenSolaris to achieve better network I/O performance in multiprocessing environments; however, network stack parallelization has also brought extra overheads for system. An effective and efficient network I/O optimization in multiprocessing environments is required to cross all levers of the network stack from network interface to application.
55533633
Building global HEP systems on Kerberos
As an underpinning of AFS and Windows 2000, and as a formally proven security protocol [1] in its own right, Kerberos is ubiquitous among HEP sites. Fermilab and users from other sites have taken advantage of this and built a diversity of distributed applications over Kerberos v5. We present several projects in which this security infrastructure has been leveraged to meet the requirements of geographically dispersed collaborations. These range from straightforward ''Kerberization'' of applications such as database and batch services, to quick tricks like simulating a user-authenticated web service with AFS and the ''file'': schema, to more complex systems. Examples of the latter include experiment control room operations and the Central Analysis Farm (CAF). We present several use cases and their security models, and examine how they attempt to address some of the outstanding problems of secure distributed computing: delegation of the least necessary privilege; establishment of trust between a user and a remote processing facility; credentials for long-queued or long-running processes, and automated processes running without any user's presence; security of remotely-stored credentials; and ability to scale to the numbers of sites, machines and users expected in the collaborations of the coming decade.
1290244
Statistical mechanics in a covariant gauge.
Many astrophysical and other problems require renormalizable field-theory calculations to be performed at nonzero temperature. An operator formalism is presented here for gauge fields coupled to scalars in the covariant X Hooft-Feynman gauge. It is shown that the introduction of projection operators into thermal averages can be avoided by a simple change in the definition of the trace operation. The partition function and finite-temperature propagators are derived in real time for spontaneously broken gauge theories.
120207464
Electron-Nuclear Potential Fields from Hyperfine Structure