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CSE421 Midterm Solutions —SOLUTION SET— 09 Mar 2012
CSE421 Midterm Solutions —SOLUTION SET— 09 Mar 2012 This midterm exam consists of three types of questions: 1. 10 multiple choice questions worth 1 point each. These are drawn directly from lecture slides and intended to be easy. 2. 6 short answer questions worth 5 points each. You can answer as many as you want, but we will give you credit for your best four answers for a total of up to 20 points. You should be able to answer the short answer questions in four or five sentences. 3. 2 long answer questions worth 20 points each. Please answer only one long answer question. If you answer both, we will only grade one. Your answer to the long answer should span a page or two. Please answer each question as clearly and succinctly as possible. Feel free to draw pic- tures or diagrams if they help you to do so. No aids of any kind are permitted. The point value assigned to each question is intended to suggest how to allocate your time. So you should work on a 5 point question for roughly 5 minutes. CSE421 Midterm Solutions 09 Mar 2012 Multiple Choice 1. (10 points) Answer all ten of the following questions. Each is worth one point. (a) In the story that GWA (Geoff) began class with on Monday, March 4th, why was the Harvard student concerned about his grade? p He never attended class. He never arrived at class on time. He usually fell asleep in class. He was using drugs. (b) All of the following are inter-process (IPC) communication mechanisms except p shared files. -
Precise Garbage Collection for C
Precise Garbage Collection for C Jon Rafkind Adam Wick John Regehr Matthew Flatt University of Utah Galois, Inc. University of Utah University of Utah [email protected] [email protected] [email protected] mfl[email protected] Abstract no-ops. The resulting program usually runs about as well as before, Magpie is a source-to-source transformation for C programs that but without the ongoing maintenance burden of manual memory enables precise garbage collection, where precise means that inte- management. In our experience, however, conservative GC works gers are not confused with pointers, and the liveness of a pointer poorly for long-running programs, such as a web server, a program- is apparent at the source level. Precise GC is primarily useful for ming environment, or an operating system kernel. For such pro- long-running programs and programs that interact with untrusted grams, conservative GC can trigger unbounded memory use due to components. In particular, we have successfully deployed precise linked lists [Boehm 2002] that manage threads and continuations; GC in the C implementation of a language run-time system that was this problem is usually due to liveness imprecision [Hirzel et al. originally designed to use conservative GC. We also report on our 2002], rather than type imprecision. Furthermore, the programs experience in transforming parts of the Linux kernel to use precise are susceptible to memory-exhaustion attack from malicious code GC instead of manual memory management. (e.g., user programs or untrusted servlets) that might be otherwise restricted through a sandbox [Wick and Flatt 2004]. Categories and Subject Descriptors D.4.2 [Storage Manage- This paper describes our design of and experience with a GC ment]: Garbage Collection for C that is less conservative. -
Man Pages Section 3 Library Interfaces and Headers
man pages section 3: Library Interfaces and Headers Part No: 816–5173–16 September 2010 Copyright © 2010, Oracle and/or its affiliates. All rights reserved. This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. If this is software or related software documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable: U.S. GOVERNMENT RIGHTS Programs, software, databases, and related documentation and technical data delivered to U.S. Government customers are “commercial computer software” or “commercial technical data” pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, the use, duplication, disclosure, modification, and adaptation shall be subject to the restrictions and license terms setforth in the applicable Government contract, and, to the extent applicable by the terms of the Government contract, the additional rights set forth in FAR 52.227-19, Commercial Computer Software License (December 2007). Oracle America, Inc., 500 Oracle Parkway, Redwood City, CA 94065. -
Operating System Support for Parallel Processes
Operating System Support for Parallel Processes Barret Rhoden Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2014-223 http://www.eecs.berkeley.edu/Pubs/TechRpts/2014/EECS-2014-223.html December 18, 2014 Copyright © 2014, by the author(s). All rights reserved. Permission 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. Operating System Support for Parallel Processes by Barret Joseph Rhoden A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Computer Science in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Eric Brewer, Chair Professor Krste Asanovi´c Professor David Culler Professor John Chuang Fall 2014 Operating System Support for Parallel Processes Copyright 2014 by Barret Joseph Rhoden 1 Abstract Operating System Support for Parallel Processes by Barret Joseph Rhoden Doctor of Philosophy in Computer Science University of California, Berkeley Professor Eric Brewer, Chair High-performance, parallel programs want uninterrupted access to physical resources. This characterization is true not only for traditional scientific computing, but also for high- priority data center applications that run on parallel processors. These applications require high, predictable performance and low latency, and they are important enough to warrant engineering effort at all levels of the software stack. -
Sched-ITS: an Interactive Tutoring System to Teach CPU Scheduling Concepts in an Operating Systems Course
Wright State University CORE Scholar Browse all Theses and Dissertations Theses and Dissertations 2017 Sched-ITS: An Interactive Tutoring System to Teach CPU Scheduling Concepts in an Operating Systems Course Bharath Kumar Koya Wright State University Follow this and additional works at: https://corescholar.libraries.wright.edu/etd_all Part of the Computer Engineering Commons, and the Computer Sciences Commons Repository Citation Koya, Bharath Kumar, "Sched-ITS: An Interactive Tutoring System to Teach CPU Scheduling Concepts in an Operating Systems Course" (2017). Browse all Theses and Dissertations. 1745. https://corescholar.libraries.wright.edu/etd_all/1745 This Thesis is brought to you for free and open access by the Theses and Dissertations at CORE Scholar. It has been accepted for inclusion in Browse all Theses and Dissertations by an authorized administrator of CORE Scholar. For more information, please contact [email protected]. SCHED – ITS: AN INTERACTIVE TUTORING SYSTEM TO TEACH CPU SCHEDULING CONCEPTS IN AN OPERATING SYSTEMS COURSE A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science By BHARATH KUMAR KOYA B.E, Andhra University, India, 2015 2017 Wright State University WRIGHT STATE UNIVERSITY GRADUATE SCHOOL April 24, 2017 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Bharath Kumar Koya ENTITLED SCHED-ITS: An Interactive Tutoring System to Teach CPU Scheduling Concepts in an Operating System Course BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQIREMENTS FOR THE DEGREE OF Master of Science. _____________________________________ Adam R. Bryant, Ph.D. Thesis Director _____________________________________ Mateen M. Rizki, Ph.D. Chair, Department of Computer Science and Engineering Committee on Final Examination _____________________________________ Adam R. -
Part I: Unix Signals
Part I: Unix Signals 1 Stopping a Program What if you run this program? int main () { while (1); printf("bye\n"); return 0; } What happens if you hit Ctl-C? Could you make Ctl-C print ªbyeº before exiting? 2-4 Signals A shell handles Ctl-C by sending the SIGINT signal to a process The sigaction() function can be used to install a signal handler See bye.c and bye2.c 5 Some Other Signals SIGHUP terminal is gone SIGQUIT please quit SIGKILL force quit (cannot handle) SIGSEGV seg fault SIGALRM timer expired SIGPIPE write to pipe with closed read end SIGCHLD child completed 6 Timers Use setitimer() to start a timer See timer.c and timer2.c... 7 Signal Handlers and Races Beware! Ð a signal handler is practically a thread Use sigprocmask() to (un)block signals See timer3.c 8 Part II: Deadlock · Conditions · Prevention · Detection 9 Deadlock is when two or more threads are waiting for an event that can only be generated by these same threads printer->Wait(); disk->Wait(); disk->Wait(); printer->Wait(); // copy from disk // copy from disk // to printer // to printer printer->Signal(); printer->Signal(); disk->Signal(); disk->Signal(); Deadlock can occur anytime threads acquire multiple resources (printers, disks, etc.), perform work, and then release their resources 10 Deadlock 11 Deadlock 12 Deadlock Examples · Linux: In-kernel memory allocator runs out of pages, causing an ªout of memory handlerº to run, which calls a function that tries to allocate a page. · Windows 2000: The OS keeps a pool of ªworker threadsº waiting to do work; one worker thread submits a job to another worker thread, but there are no free worker-thread slots. -
Automatic Handling of Global Variables for Multi-Threaded MPI Programs
Automatic Handling of Global Variables for Multi-threaded MPI Programs Gengbin Zheng, Stas Negara, Celso L. Mendes, Laxmikant V. Kale´ Eduardo R. Rodrigues Department of Computer Science Institute of Informatics University of Illinois at Urbana-Champaign Federal University of Rio Grande do Sul Urbana, IL 61801, USA Porto Alegre, Brazil fgzheng,snegara2,cmendes,[email protected] [email protected] Abstract— necessary to privatize global and static variables to ensure Hybrid programming models, such as MPI combined with the thread-safety of an application. threads, are one of the most efficient ways to write parallel ap- In high-performance computing, one way to exploit multi- plications for current machines comprising multi-socket/multi- core nodes and an interconnection network. Global variables in core platforms is to adopt hybrid programming models that legacy MPI applications, however, present a challenge because combine MPI with threads, where different programming they may be accessed by multiple MPI threads simultaneously. models are used to address issues such as multiple threads Thus, transforming legacy MPI applications to be thread-safe per core, decreasing amount of memory per core, load in order to exploit multi-core architectures requires proper imbalance, etc. When porting legacy MPI applications to handling of global variables. In this paper, we present three approaches to eliminate these hybrid models that involve multiple threads, thread- global variables to ensure thread-safety for an MPI program. safety of the applications needs to be addressed again. These approaches include: (a) a compiler-based refactoring Global variables cause no problem with traditional MPI technique, using a Photran-based tool as an example, which implementations, since each process image contains a sep- automates the source-to-source transformation for programs arate instance of the variable. -
Scheduling: Introduction
7 Scheduling: Introduction By now low-level mechanisms of running processes (e.g., context switch- ing) should be clear; if they are not, go back a chapter or two, and read the description of how that stuff works again. However, we have yet to un- derstand the high-level policies that an OS scheduler employs. We will now do just that, presenting a series of scheduling policies (sometimes called disciplines) that various smart and hard-working people have de- veloped over the years. The origins of scheduling, in fact, predate computer systems; early approaches were taken from the field of operations management and ap- plied to computers. This reality should be no surprise: assembly lines and many other human endeavors also require scheduling, and many of the same concerns exist therein, including a laser-like desire for efficiency. And thus, our problem: THE CRUX: HOW TO DEVELOP SCHEDULING POLICY How should we develop a basic framework for thinking about scheduling policies? What are the key assumptions? What metrics are important? What basic approaches have been used in the earliest of com- puter systems? 7.1 Workload Assumptions Before getting into the range of possible policies, let us first make a number of simplifying assumptions about the processes running in the system, sometimes collectively called the workload. Determining the workload is a critical part of building policies, and the more you know about workload, the more fine-tuned your policy can be. The workload assumptions we make here are mostly unrealistic, but that is alright (for now), because we will relax them as we go, and even- tually develop what we will refer to as .. -
Threading and GUI Issues for R
Threading and GUI Issues for R Luke Tierney School of Statistics University of Minnesota March 5, 2001 Contents 1 Introduction 2 2 Concurrency and Parallelism 2 3 Concurrency and Dynamic State 3 3.1 Options Settings . 3 3.2 User Defined Options . 5 3.3 Devices and Par Settings . 5 3.4 Standard Connections . 6 3.5 The Context Stack . 6 3.5.1 Synchronization . 6 4 GUI Events And Blocking IO 6 4.1 UNIX Issues . 7 4.2 Win32 Issues . 7 4.3 Classic MacOS Issues . 8 4.4 Implementations To Consider . 8 4.5 A Note On Java . 8 4.6 A Strategy for GUI/IO Management . 9 4.7 A Sample Implementation . 9 5 Threads and GUI’s 10 6 Threading Design Space 11 6.1 Parallelism Through HL Threads: The MXM Options . 12 6.2 Light-Weight Threads: The XMX Options . 12 6.3 Multiple OS Threads Running One At A Time: MSS . 14 6.4 Variations on OS Threads . 14 6.5 SMS or MXS: Which To Choose? . 14 7 Light-Weight Thread Implementation 14 1 March 5, 2001 2 8 Other Issues 15 8.1 High-Level GUI Interfaces . 16 8.2 High-Level Thread Interfaces . 16 8.3 High-Level Streams Interfaces . 16 8.4 Completely Random Stuff . 16 1 Introduction This document collects some random thoughts on runtime issues relating to concurrency, threads, GUI’s and the like. Some of this is extracted from recent R-core email threads. I’ve tried to provide lots of references that might be of use. -
KAAPI: a Thread Scheduling Runtime System for Data Flow Computations
KAAPI: A thread scheduling runtime system for data flow computations on cluster of multi-processors Thierry Gautier, Xavier Besseron, Laurent Pigeon INRIA, projet MOAIS LIG, Batiment^ ENSIMAG 51 avenue Jean-Kuntzmann F-38330 Montbonnot St Martin, France [email protected], [email protected], [email protected] ABSTRACT among the processors. In the work-stealing scheduling [7], The high availability of multiprocessor clusters for com- each processor gets its own stack implemented by a deque puter science seems to be very attractive to the engineer of frames. When a thread is created, a new frame is ini- because, at a first level, such computers aggregate high per- tialized and pushed at the bottom of the deque. When a formances. Nevertheless, obtaining peak performances on processor become idle, it tries to steal work from a victim irregular applications such as computer algebra problems re- processor with a non-empty deque; then it takes the top- mains a challenging problem. The delay to access memory is most frame (the least recently pushed frame) and places it non uniform and the irregularity of computations requires to in its own deque which is linked to the victim deque. use scheduling algorithms in order to automatically balance Such scheduling has been proven to be efficient for fully- the workload among the processors. strict multithreaded computations [7, 12] while requiring a This paper focuses on the runtime support implementa- bounded memory space with respect to a depth first sequen- tion to exploit with great efficiency the computation re- tial execution [8, 29]. sources of a multiprocessor cluster. -
Brocade Fabric OS Administration Guide, 8.2.1
ADMINISTRATION GUIDE Brocade Fabric OS Administration Guide, 8.2.1 Supporting Fabric OS 8.2.1 FOS-821-AG101 28 September 2018 Copyright © 2018 Brocade Communications Systems LLC. All Rights Reserved. Brocade and the stylized B logo are among the trademarks of Brocade Communications Systems LLC. Broadcom, the pulse logo, and Connecting everything are among the trademarks of Broadcom. The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries. Brocade, a Broadcom Inc. Company, reserves the right to make changes without further notice to any products or data herein to improve reliability, function, or design. Information furnished by Brocade is believed to be accurate and reliable. However, Brocade does not assume any liability arising out of the application or use of this information, nor the application or use of any product or circuit described herein, neither does it convey any license under its patent rights nor the rights of others. The product described by this document may contain open source software covered by the GNU General Public License or other open source license agreements. To find out which open source software is included in Brocade products, view the licensing terms applicable to the open source software, and obtain a copy of the programming source code, please visit https://www.broadcom.com/support/fibre-channel-networking/tools/oscd. Brocade Fabric OS Administration Guide, 8.2.1 2 FOS-821-AG101 Contents Introduction........................................................................................................................................................................................................................18 -
ELC PLATFORM SPECIFICATION Version 1.0
! ! ! ! !"# $"%&'()*+,$!#-'-#%&-(. /012345+678 "##$%&'()*'+',-'$).//. &90+!:;0<<0<+"35=>+#45241?3=: ! ! CONTENTS 1 Copyright and Licensing Terms...........................................................................................1 2 Acknowledgements.............................................................................................................1 3 Introduction.................................................................................................................. .......2 3.1 Purpose .......................................................................................................................2 3.2 Relationship to Other Industry Standards.....................................................................3 3.3 How To Use This Specification ...................................................................................4 3.4 Definitions...................................................................................................................4 3.4.1 ELCPS.................................................................................................................4 3.4.2 ELCPS-Compliant Application............................................................................4 3.4.3 ELCPS-Conforming Implementation ...................................................................4 3.4.4 Non-ELCPS-Compliant Application....................................................................5 3.4.5 ELCPS Implementation Conformance .................................................................5 3.4.6