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Membrane: Operating System Support for Restartable File Systems Swaminathan Sundararaman, Sriram Subramanian, Abhishek Rajimwale, Andrea C
Membrane: Operating System Support for Restartable File Systems Swaminathan Sundararaman, Sriram Subramanian, Abhishek Rajimwale, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau, Michael M. Swift Computer Sciences Department, University of Wisconsin, Madison Abstract and most complex code bases in the kernel. Further, We introduce Membrane, a set of changes to the oper- file systems are still under active development, and new ating system to support restartable file systems. Mem- ones are introduced quite frequently. For example, Linux brane allows an operating system to tolerate a broad has many established file systems, including ext2 [34], class of file system failures and does so while remain- ext3 [35], reiserfs [27], and still there is great interest in ing transparent to running applications; upon failure, the next-generation file systems such as Linux ext4 and btrfs. file system restarts, its state is restored, and pending ap- Thus, file systems are large, complex, and under develop- plication requests are serviced as if no failure had oc- ment, the perfect storm for numerous bugs to arise. curred. Membrane provides transparent recovery through Because of the likely presence of flaws in their imple- a lightweight logging and checkpoint infrastructure, and mentation, it is critical to consider how to recover from includes novel techniques to improve performance and file system crashes as well. Unfortunately, we cannot di- correctness of its fault-anticipation and recovery machin- rectly apply previous work from the device-driver litera- ery. We tested Membrane with ext2, ext3, and VFAT. ture to improving file-system fault recovery. File systems, Through experimentation, we show that Membrane in- unlike device drivers, are extremely stateful, as they man- duces little performance overhead and can tolerate a wide age vast amounts of both in-memory and persistent data; range of file system crashes. -
HOW FAST IS RF? by RON HRANAC
Originally appeared in the September 2008 issue of Communications Technology. HOW FAST IS RF? By RON HRANAC Maybe a better question is, "What's the speed of an electromagnetic signal in a vacuum?" After all, what we call RF refers to signals in the lower frequency or longer wavelength part of the electromagnetic spectrum. Light is an electromagnetic signal, too, existing in the higher frequency or shorter wavelength part of the electromagnetic spectrum. One way to look at it is to assume that RF is nothing more than really, really low frequency light, or that light is really, really high frequency RF. As you might imagine, the numbers involved in describing RF and light can be very large or very small. For more on this, see my June 2007 CT column, "Big Numbers, Small Numbers" (www.cable360.net/ct/operations/techtalk/23783.html). According to the National Institute of Standards and Technology, the speed of light in a vacuum, c0, is 299,792,458 meters per second (http://physics.nist.gov/cgi-bin/cuu/Value?c). The designation c0 is one that NIST uses to reference the speed of light in a vacuum, while c is occasionally used to reference the speed of light in some other medium. Most of the time the subscript zero is dropped, with c being a generic designation for the speed of light. Let's put c0 in terms that may be more familiar. You probably recall from junior high or high school science class that the speed of light is 186,000 miles per second. -
Reference Modification Error in Cobol
Reference Modification Error In Cobol Bartholomeus freeze-dries her Burnley when, she objurgates it atilt. Luke still brutalize prehistorically while rosaceous Dannie aphorizing that luncheonettes. When Vernor splashes his exobiologists bronzing not histrionically enough, is Efram attrite? The content following a Kubernetes template file. Work during data items. Those advice are consolidated, transformed and made sure for the mining and online processing. For post, if internal programs A and B are agile in a containing program and A calls B and B cancels A, this message will be issued. Charles Phillips to demonstrate his displeasure. The starting position itself must man a positive integer less than one equal possess the saw of characters in the reference modified function result. Always some need me give when in quotes. Cobol reference an error will open a cobol reference modification error in. The MOVE command transfers data beyond one specimen of storage to another. Various numeric intrinsic functions are also mentioned. Is there capital available version of the rpg programming language available secure the PC? Qualification, reference modification, and subscripting or indexing allow blood and unambiguous references to that resource. Writer was slated to be shown at the bass strings should be. Handle this may be sorted and a precision floating point in sequential data transfer be from attacks in virtually present before performing a reference modification starting position were a statement? What strength the difference between index and subscript? The sum nor the leftmost character position and does length must not made the total length form the character item. Shown at or of cobol specification was slated to newspaper to get rid once the way. -
Low Latency – How Low Can You Go?
WHITE PAPER Low Latency – How Low Can You Go? Low latency has always been an important consideration in telecom networks for voice, video, and data, but recent changes in applications within many industry sectors have brought low latency right to the forefront of the industry. The finance industry and algorithmic trading in particular, or algo-trading as it is known, is a commonly quoted example. Here latency is critical, and to quote Information Week magazine, “A 1-millisecond advantage in trading applications can be worth $100 million a year to a major brokerage firm.” This drives a huge focus on all aspects of latency, including the communications systems between the brokerage firm and the exchange. However, while the finance industry is spending a lot of money on low- latency services between key locations such as New York and Chicago or London and Frankfurt, this is actually only a small part of the wider telecom industry. Many other industries are also now driving lower and lower latency in their networks, such as for cloud computing and video services. Also, as mobile operators start to roll out 5G services, latency in the xHaul mobile transport network, especially the demanding fronthaul domain, becomes more and more important in order to reach the stringent 5G requirements required for the new class of ultra-reliable low-latency services. This white paper will address the drivers behind the recent rush to low- latency solutions and networks and will consider how network operators can remove as much latency as possible from their networks as they also race to zero latency. -
Timestamp Precision
Timestamp Precision Kevin Bross 15 April 2016 15 April 2016 IEEE 1904 Access Networks Working Group, San Jose, CA USA 1 Timestamp Packets The orderInfo field can be used as a 32-bit timestamp, down to ¼ ns granularity: 1 s 30 bits of nanoseconds 2 ¼ ms µs ns ns Two main uses of timestamp: – Indicating start or end time of flow – Indicating presentation time of packets for flows with non-constant data rates s = second ms = millisecond µs = microsecond ns = nanosecond 15 April 2016 IEEE 1904 Access Networks Working Group, San Jose, CA USA 2 Presentation Time To reduce bandwidth during idle periods, some protocols will have variable rates – Fronthaul may be variable, even if rate to radio unit itself is a constant rate Presentation times allows RoE to handle variable data rates – Data may experience jitter in network – Egress buffer compensates for network jitter – Presentation time is when the data is to exit the RoE node • Jitter cleaners ensure data comes out cleanly, and on the right bit period 15 April 2016 IEEE 1904 Access Networks Working Group, San Jose, CA USA 3 Jitter vs. Synchronization Synchronization requirements for LTE are only down to ~±65 ns accuracy – Each RoE node may be off from TAI by up to 65 ns (or more in some circumstances) – Starting and ending a stream may be off by this amount …but jitter from packet to packet must be much tighter – RoE nodes should be able to output data at precise relative times if timestamp is used for a given packet – Relative bit time within a flow is important 15 April 2016 IEEE 1904 Access -
Process Scheduling
PROCESS SCHEDULING ANIRUDH JAYAKUMAR LAST TIME • Build a customized Linux Kernel from source • System call implementation • Interrupts and Interrupt Handlers TODAY’S SESSION • Process Management • Process Scheduling PROCESSES • “ a program in execution” • An active program with related resources (instructions and data) • Short lived ( “pwd” executed from terminal) or long-lived (SSH service running as a background process) • A.K.A tasks – the kernel’s point of view • Fundamental abstraction in Unix THREADS • Objects of activity within the process • One or more threads within a process • Asynchronous execution • Each thread includes a unique PC, process stack, and set of processor registers • Kernel schedules individual threads, not processes • tasks are Linux threads (a.k.a kernel threads) TASK REPRESENTATION • The kernel maintains info about each process in a process descriptor, of type task_struct • See include/linux/sched.h • Each task descriptor contains info such as run-state of process, address space, list of open files, process priority etc • The kernel stores the list of processes in a circular doubly linked list called the task list. TASK LIST • struct list_head tasks; • init the "mother of all processes” – statically allocated • extern struct task_struct init_task; • for_each_process() - iterates over the entire task list • next_task() - returns the next task in the list PROCESS STATE • TASK_RUNNING: running or on a run-queue waiting to run • TASK_INTERRUPTIBLE: sleeping, waiting for some event to happen; awakes prematurely if it receives a signal • TASK_UNINTERRUPTIBLE: identical to TASK_INTERRUPTIBLE except it ignores signals • TASK_ZOMBIE: The task has terminated, but its parent has not yet issued a wait4(). The task's process descriptor must remain in case the parent wants to access it. -
Discovery of Frequency-Sweeping Millisecond Solar Radio Bursts Near 1400 Mhz with a Small Interferometer Physics Department Senior Honors Thesis 2006 Eric R
Discovery of frequency-sweeping millisecond solar radio bursts near 1400 MHz with a small interferometer Physics Department Senior Honors Thesis 2006 Eric R. Evarts Brandeis University Abstract While testing the Small Radio Telescope Interferometer at Haystack Observatory, we noticed occasional strong fringes on the Sun. Upon closer study of this activity, I find that each significant burst corresponds to an X-ray solar flare and corresponds to data observed by RSTN. At very short integrations (512 µs), most bursts disappear in the noise, but a few still show very strong fringes. Studying these <25 events at 512 µs integration reveals 2 types of burst: one with frequency structure and one without. Bursts with frequency structure have a brightness temperature ~1013K, while bursts without frequency structure have a brightness temperature ~108K. These bursts are studied at higher frequency resolution than any previous solar study revealing a very distinct structure that is not currently understood. 1 Table of Contents Abstract ..........................................................................................................................1 Table of Contents...........................................................................................................3 Introduction ...................................................................................................................5 Interferometry Crash Course ........................................................................................5 The Small Radio Telescope -
HP Decnet-Plus for Openvms Decdts Management
HP DECnet-Plus for OpenVMS DECdts Management Part Number: BA406-90003 January 2005 This manual introduces HP DECnet-Plus Distributed Time Service (DECdts) concepts and describes how to manage the software and system clocks. Revision/Update Information: This manual supersedes DECnet-Plus DECdts Management (AA-PHELC-TE). Operating Systems: OpenVMS I64 Version 8.2 OpenVMS Alpha Version 8.2 Software Version: HP DECnet-Plus for OpenVMS Version 8.2 HP DECnet-Plus Distributed Time Service Version 2.0 Hewlett-Packard Company Palo Alto, California © Copyright 2005 Hewlett-Packard Development Company, L.P. Confidential computer software. Valid license from HP required for possession, use, or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor’s standard commercial license. The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein. Intel and Itanium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. UNIX is a registered trademark of The Open Group. Printed in the US Contents Preface ............................................................ vii 1 Introduction to the HP DECnet-Plus Distributed Time Service 1.1 DECdts Advantages . ........................................ 1–2 1.1.1 Applications Support ...................................... 1–2 1.1.2 External Time-Provider Support ............................ -
Microsecond and Millisecond Dynamics in the Photosynthetic
Microsecond and millisecond dynamics in the photosynthetic protein LHCSR1 observed by single-molecule correlation spectroscopy Toru Kondoa,1,2, Jesse B. Gordona, Alberta Pinnolab,c, Luca Dall’Ostob, Roberto Bassib, and Gabriela S. Schlau-Cohena,1 aDepartment of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139; bDepartment of Biotechnology, University of Verona, 37134 Verona, Italy; and cDepartment of Biology and Biotechnology, University of Pavia, 27100 Pavia, Italy Edited by Catherine J. Murphy, University of Illinois at Urbana–Champaign, Urbana, IL, and approved April 11, 2019 (received for review December 13, 2018) Biological systems are subjected to continuous environmental (5–9) or intensity correlation function analysis (10). CPF analysis fluctuations, and therefore, flexibility in the structure and func- bins the photon data, obscuring fast dynamics. In contrast, inten- tion of their protein building blocks is essential for survival. sity correlation function analysis characterizes fluctuations in the Protein dynamics are often local conformational changes, which photon arrival rate, accessing dynamics down to microseconds. allows multiple dynamical processes to occur simultaneously and However, the fluorescence lifetime is a powerful indicator of rapidly in individual proteins. Experiments often average over conformation for chromoproteins and for lifetime-based FRET these dynamics and their multiplicity, preventing identification measurements, yet it is ignored in intensity-based analyses. of the molecular origin and impact on biological function. Green 2D fluorescence lifetime correlation (2D-FLC) analysis was plants survive under high light by quenching excess energy, recently introduced as a method to both resolve fast dynam- and Light-Harvesting Complex Stress Related 1 (LHCSR1) is the ics and use fluorescence lifetime information (11, 12). -
Challenges Using Linux As a Real-Time Operating System
https://ntrs.nasa.gov/search.jsp?R=20200002390 2020-05-24T04:26:54+00:00Z View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by NASA Technical Reports Server Challenges Using Linux as a Real-Time Operating System Michael M. Madden* NASA Langley Research Center, Hampton, VA, 23681 Human-in-the-loop (HITL) simulation groups at NASA and the Air Force Research Lab have been using Linux as a real-time operating system (RTOS) for over a decade. More recently, SpaceX has revealed that it is using Linux as an RTOS for its Falcon launch vehicles and Dragon capsules. As Linux makes its way from ground facilities to flight critical systems, it is necessary to recognize that the real-time capabilities in Linux are cobbled onto a kernel architecture designed for general purpose computing. The Linux kernel contain numerous design decisions that favor throughput over determinism and latency. These decisions often require workarounds in the application or customization of the kernel to restore a high probability that Linux will achieve deadlines. I. Introduction he human-in-the-loop (HITL) simulation groups at the NASA Langley Research Center and the Air Force TResearch Lab have used Linux as a real-time operating system (RTOS) for over a decade [1, 2]. More recently, SpaceX has revealed that it is using Linux as an RTOS for its Falcon launch vehicles and Dragon capsules [3]. Reference 2 examined an early version of the Linux Kernel for real-time applications and, using black box testing of jitter, found it suitable when paired with an external hardware interval timer. -
The Effect of Long Timescale Gas Dynamics on Femtosecond Filamentation
The effect of long timescale gas dynamics on femtosecond filamentation Y.-H. Cheng, J. K. Wahlstrand, N. Jhajj, and H. M. Milchberg* Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA *[email protected] Abstract: Femtosecond laser pulses filamenting in various gases are shown to generate long- lived quasi-stationary cylindrical depressions or ‘holes’ in the gas density. For our experimental conditions, these holes range up to several hundred microns in diameter with gas density depressions up to ~20%. The holes decay by thermal diffusion on millisecond timescales. We show that high repetition rate filamentation and supercontinuum generation can be strongly affected by these holes, which should also affect all other experiments employing intense high repetition rate laser pulses interacting with gases. ©2013 Optical Society of America OCIS codes: (190.5530) Pulse propagation and temporal solitons; (350.6830) Thermal lensing; (320.6629) Supercontinuum generation; (260.5950) Self-focusing. References and Links 1. A. Couairon and A. Mysyrowicz, “Femtosecond filamentation in transparent media,” Phys. Rep. 441(2-4), 47– 189 (2007). 2. P. B. Corkum, C. Rolland, and T. Srinivasan-Rao, “Supercontinuum generation in gases,” Phys. Rev. Lett. 57(18), 2268–2271 (1986). S. A. Trushin, K. Kosma, W. Fuss, and W. E. Schmid, “Sub-10-fs supercontinuum radiation generated by filamentation of few-cycle 800 nm pulses in argon,” Opt. Lett. 32(16), 2432–2434 (2007). 3. N. Zhavoronkov, “Efficient spectral conversion and temporal compression of femtosecond pulses in SF6.,” Opt. Lett. 36(4), 529–531 (2011). 4. C. P. Hauri, R. B. -
Dose-Adjusted Epoch and Rituximab for the Treatment of Double
Dose-Adjusted Epoch and Rituximab for the treatment of double expressor and double hit diffuse large B-cell lymphoma: impact of TP53 mutations on clinical outcome by Anna Dodero, Anna Guidetti, Fabrizio Marino, Alessandra Tucci, Francesco Barretta, Alessandro Re, Monica Balzarotti, Cristiana Carniti, Chiara Monfrini, Annalisa Chiappella, Antonello Cabras, Fabio Facchetti, Martina Pennisi, Daoud Rahal, Valentina Monti, Liliana Devizzi, Rosalba Miceli, Federica Cocito, Lucia Farina, Francesca Ricci, Giuseppe Rossi, Carmelo Carlo-Stella, and Paolo Corradini Haematologica. 2021; Jul 22. doi: 10.3324/haematol.2021.278638 [Epub ahead of print] Received: February 26, 2021. Accepted: July 13, 2021. Citation: Anna Dodero, Anna Guidetti, Fabrizio Marino, Alessandra Tucci, Francesco Barretta, Alessandro Re, Monica Balzarotti, Cristiana Carniti, Chiara Monfrini, Annalisa Chiappella, Antonello Cabras, Fabio Facchetti, Martina Pennisi, Daoud Rahal, Valentina Monti, Liliana Devizzi, Rosalba Miceli, Federica Cocito, Lucia Farina, Francesca Ricci, Giuseppe Rossi, Carmelo Carlo-Stella, and Paolo Corradini. Dose-Adjusted Epoch and Rituximab for the treatment of double expressor and double hit d fuse large B-cell lymphoma: impact of TP53 mutations on clinical outcome. Publisher's Disclaimer. E-publishing ahead of print is increasingly important for the rapid dissemination of science. Haematologica is, therefore, E-publishing PDF files of an early version of manuscripts that have completed a regular peer review and have been accepted for publication. E-publishing of this PDF file has been approved by the authors. After having E-published Ahead of Print, manuscripts will then undergo technical and English editing, typesetting, proof correction and be presented for the authors' final approval; the final version of the manuscript will then appear in a regular issue of the journal.