DOCSLIB.ORG

Journal : Linux: Une Décennie De Coeurs Gaspillés Posté Par Pmoret (Page Perso) Le 08/04/16 À 09:30

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Journal : Linux: Une Décennie De Coeurs Gaspillés Posté Par Pmoret (Page Perso) Le 08/04/16 À 09:30 Journal : Linux: une décennie de coeurs gaspillés Posté par pmoret (page perso) le 08/04/16 à 09:30. Licence CC by-sa Tags : linux, scheduler D'aucuns pensaient que l'ordonnancement (scheduling) était un problème résolu ou presque. Linus Torvals disait en 2001: And you have to realize that there are not very many things that have aged as well as the scheduler. Which is just another proof that scheduling is easy. Vous devez réaliser que peu de choses ont aussi bien vieilli que l'ordonnanceur. Ce qui constitue une preuve de plus que l'ordonnancement est facile. L'implémentation pratique d'un algorithme pour les systèmes multi-coeurs est cependant loin d'être triviale. La publication qui donne lieu à ce journal The Linux Scheduler: a Decade of Wasted Cores l'illustre sur plusieurs points. La parution de ce journal un vendredi est bien entendu une pure coïncidence. En résumé, la problématique est que le coût de transfert d'un process vers un autre coeur est potentiellement élevé, et dépend entre autre de la structure des mémoires cache. L'agrégation des données de charge entre les coeurs/processeurs doit aussi être réfléchie, il y a un équilibre à trouver entre trop partager entre les coeurs et ralentir le système et risquer de prendre des décisions d'ordonnancement basées sur des informations partielles. Il y a donc recours à des heuristiques et optimisations qui ne fonctionnent pas dans tous les cas: dans la publication il est montré que certains coeurs sont inactifs pour de longues période alors que des processus prêts à tourner attendent ailleurs. L'article se lit bien et est agrémenté de citations de notre cher Linus qui n'a pas toujours raison… Energy waste is proportional. Posté par mh-cbon le 08/04/16 à 10:13. Évalué à -8 (+11/-15). +1 à main levée, comme je n'ai plus de droit de vote ; ) Re: Energy waste is proportional. Posté par Dr. Frank N. Furter le 08/04/16 à 10:21. Évalué à 8 (+6/-0). https://linuxfr.org/aide#aide-karma -- Depending on the time of day, the French go either way. Re: Energy waste is proportional. Posté par mh-cbon le 08/04/16 à 10:29. Évalué à -6 (+4/-6). Pour pouvoir écrire un journal, dans le wiki ou sur la tribune, il faut avoir un karma supérieur strictement à 0 (sources journal, wiki, tribune). autant dire que c'est mort pour moi pour le moment :D Et bon bah, je ne te mettrais pas +1 pour contribuer à ton karma vu que je ne peux plus voter :=/ J'aimerais bien connaitre ma valeur de karma. Pour en revenir sur le papier, on s'amuse beaucoup à lire les citations ;) Par contre la partie explicative de l’ordonnancement en multi-coeur nécessitera plus d'une re-lecture, donc au moins 3 lectures en ce qui me concerne. Re: Energy waste is proportional. Posté par Dr. Frank N. Furter le 08/04/16 à 10:48. Évalué à 9 (+7/-0). […]Le karma augmente donc lorsque l'on reçoit des notes « pertinent » (quel que soit le type de contenu ou le commentaire noté) ou que l'on publie des dépêches. J'aimerais bien connaitre ma valeur de karma. https://linuxfr.org/users/mh-cbon 3eme boite sur la gauche. -- Depending on the time of day, the French go either way. Ouai... Posté par barmic le 08/04/16 à 10:20. Évalué à 10 (+7/-0). D'aucuns pensaient que l'ordonnancement (scheduling) était un problème résolu ou presque. Linus Torvals disait en 2001: Puis en 2007, le noyau a totalement changé de scheduler pour passer à CFS (les cgroups, LXC, Docker, systemd, ça parle à des gens ? ;) ) et c'était tellement limpide qu'il y toujours eu un concurrent de CFS : BFS (pour Brain Fuck Scheduler W). D'après son maintenant, quand tu a moins de 16 cores son truc est mieux (j'en profite pour découvrir que c'est encore maintenu ce qui est cool :). J'ai pas lu l'article mais par rapport à ce que tu dis. Grosso modo le problème des schedulers, c'est qu'ils doivent prendre en un temps très réduit une décision sans pour autant avoir toutes les informations dont ils ont besoin à disposition. Le noyau a toujours (ou depuis très longtemps) eu de quoi interagir avec l'ordonnanceur depuis le userspace (avec cpuset par exemple), mais CFS via les cgroups a apporté beaucoup plus de finesse dans cela. Pour rappel 3 ans après sont introduction, on a eu une nouvelle option dans le noyau qui montrait bien l'intérêt de CFS : http://www.computerworld.com/article/2469655/desktop-apps/the-linux-desktop-may-soon-be-a-lot-faster.html Bref en 2001, il restait encore beaucoup à faire ! :) -- Les logiciels sous licence GPL forcent leurs utilisateurs à respecter la GPL (et oui, l'eau, ça mouille). However, they must be able to steal from the more loaded cores on other nodes. Posté par mh-cbon le 08/04/16 à 10:40. Évalué à -9 (+1/-6). Why is this not the case? Remember that to limit algorithmic complexity, the load balancing algorithm uses a hierarchical design. When a core attempts to steal work from another node, or, in other words, from another scheduling group, it does not examine the load of every core in that group, it only looks at the group’s average load (line 11 of Algorithm 1). If the average load of the victim scheduling group is greater than that of its own, it will attempt to steal from that group; otherwise it will not. This is the exact reason why in our situation the underloaded cores fail to steal from the overloaded cores on other nodes. They observe that the average load of the victim node’s scheduling group is not any greater than their own. The core trying to steal work runs on the same node as the high-load R thread; that thread skews up the average load for that node and conceals the fact that some cores are actually idle. At the same time, cores on the victim node, with roughly the same average load, have lots of waiting threads. Re: However, they must be able to steal from the more loaded cores on other nodes. Posté par ʭ ☯ (page perso) le 08/04/16 à 10:51. Évalué à -2 (+0/-4). Même traduit automatiquement ça ne devient pas compréhensible en français ;-) Pourquoi est-ce pas le cas? Rappelez-vous que pour limiter la complexité algorithmique, la charge algorithme d'équilibrage utilise une conception hiérarchique. Quand un noyau les tentatives de voler le travail d'un autre noeud, ou, en d'autres termes, d'un autre groupe de planification, il ne porte pas sur la charge de chaque noyau de ce groupe, il ne regarde que le groupe de charge moyenne (ligne 11 de l'algorithme 1). Si la charge moyenne du groupe de planification de la victime est supérieure à celle de son propre, il va tenter de voler de ce groupe; sinon ne sera pas. Ceci est la raison exacte pour laquelle dans notre situation, la noyaux sous-charge ne parviennent pas à voler les noyaux surchargés sur d'autres nœuds. Ils observent que la charge moyenne de la victime noeuds groupe de planification est pas plus grande que leur posséder. Le noyau essayant de voler le travail fonctionne sur le même noeud le R-fil de charge élevée; ce fil biaise la moyenne charger pour ce noeud et cache le fait que certains noyaux sont effectivement ralenti. Dans le même temps, les noyaux sur le noeud victime, avec à peu près la même charge moyenne, ont beaucoup d'attente threads. -- ⚓ À g'Auch TOUTE! http://agauch.online.fr Re: However, they must be able to steal from the more loaded cores on other nodes. Posté par mh-cbon le 08/04/16 à 11:13. Évalué à -7 (+1/-4). oui, et puis je ne m'y tenterais pas. Le portage de certaines dénominations de la langue anglaise vers la langue française sont vraiment insupportable. Mon plus bel exemple étant celui ci Projects each element of an observable sequence into a new sequence of observable sequences by incorporating the element's index and then transforms an observable sequence of observable sequences into an observable sequence producing values only from the most recent observable sequence. tenter le en traduisant observable par sujet, vous allez voir c'est pas fun ; ) Ceci dit, c'était surtout pour réagir à ceci, mais la citation était mal choisie. Le noyau a toujours (ou depuis très longtemps) eu de quoi interagir avec l'ordonnanceur depuis le userspace (avec cpuset par exemple), mais CFS via les cgroups a apporté beaucoup plus de finesse dans cela. Je saute aux conclusions (j'avoue je n'ai pas lu tous les bugs), le problème n'est pas le manque d'outils existant ou d'algo, mais leurs intégrations dans un système fiable et cohérent. All of these algorithms (le papier en cite plusieurs pour diverses optimisations) showed positive benefits, either in terms of performance or power, for some real applications. However, few of them were adopted in mainstream operating systems, mainly because it is not clear how to integrate all these ideas in scheduler safely. Pour réussir ce véritable défi, le papier préconise de commencer par se doter d'outils de visualisation. Another lesson we learned as a result of this work is the crucial importance of visualization tools.
Load more

Recommended publications
  • Embedded Systems
    Sri Chandrasekharendra Saraswathi Viswa Maha Vidyalaya Department of Electronics and Communication Engineering STUDY MATERIAL for III rd Year VI th Semester Subject Name: EMBEDDED SYSTEMS Prepared by Dr.P.Venkatesan, Associate Professor, ECE, SCSVMV University Sri Chandrasekharendra Saraswathi Viswa Maha Vidyalaya Department of Electronics and Communication Engineering PRE-REQUISITE: Basic knowledge of Microprocessors, Microcontrollers & Digital System Design OBJECTIVES: The student should be made to – Learn the architecture and programming of ARM processor. Be familiar with the embedded computing platform design and analysis. Be exposed to the basic concepts and overview of real time Operating system. Learn the system design techniques and networks for embedded systems to industrial applications. Sri Chandrasekharendra Saraswathi Viswa Maha Vidyalaya Department of Electronics and Communication Engineering SYLLABUS UNIT – I INTRODUCTION TO EMBEDDED COMPUTING AND ARM PROCESSORS Complex systems and micro processors– Embedded system design process –Design example: Model train controller- Instruction sets preliminaries - ARM Processor – CPU: programming input and output- supervisor mode, exceptions and traps – Co- processors- Memory system mechanisms – CPU performance- CPU power consumption. UNIT – II EMBEDDED COMPUTING PLATFORM DESIGN The CPU Bus-Memory devices and systems–Designing with computing platforms – consumer electronics architecture – platform-level performance analysis - Components for embedded programs- Models of programs-
    [Show full text]
  • 1999 Nendo Supercompiler Te
    NEDO-PR- 9 90 3 x-A°-=i wu ? '7-z / □ ixomgffi'g. NEDOBIS T93018 #f%4vl/4=- — 'I'Jff&'a fi ISEDQ mb'Sa 3a 0-7 rx-/<-n>/<^7-T^yovOIElS9f%l TR&1 2^3^ A 249H illK t>*^#itafc?iJI+WE$>i=t^<bLfc3>/U7S#r$u:|-^n S & - *%#$............. (3) (5) m #.......... (7) Abstract............ (9) m #?'Hb3>/W3## i 1.1 # i 1.2 g ##Wb3 7 ©&ffitib[p].................................................... 3 1.2.1 ............................................................................... 3 1.2.2 ^ y ........................................................................ 18 1.2.3 OpenMP 43,fctf OpenMP ©x-^fcKlfOttfcifeSi................. 26 1.2.4 #%3 >;W ly —^ 3 .............................................. 39 1.2.5 VLIW ^;i/3£#Hb.................................................................... 48 1.2.6 ........................ 62 1.2.7 3>;W7 <b)## p/i-f-zL —- > py—............... 72 1.2.8 3 >;w 3©##E#m©##mm.............................................. 82 1.2.9 3°3-tr y +1 © lb fp] : Stanford Hydra Chip Multiprocessor 95 1.2.10 s^^Eibrniiis : hpca -6 .............................. 134 1.3 # b#^Hb3>/W7^#m%................. 144 1.3.1 m # 144 1.3.2 145 1.3.3 m 152 1.3.4 152 2$ j£M^>E3 >hajL-T-^ 155 2.1 M E......................................................................................................................... 155 2.2 j£M5>i(3 > b° j-—x 4“ >^"©&Hlib[p] ........................................................... 157 2.2.. 1 j[£WtS(3>h0a.-:r^ >^'©51^............................................................ 157 2.2.2 : Grid Forum99, U.C.B., JavaGrande Portals Group Meeting iZjotf & ti^jSbfp] — 165 2.2.3 : Supercomputing99 iZlotf & ££l/tribip].................... 182 2.2.4 Grid##43Z^^m^m^^7"A Globus ^©^tn1 G: Hit* £ tiWSbfp] ---- 200 (1) 2.3 ><y(D mmtmrn......
    [Show full text]
  • Thread Scheduling in Multi-Core Operating Systems Redha Gouicem
    Thread Scheduling in Multi-core Operating Systems Redha Gouicem To cite this version: Redha Gouicem. Thread Scheduling in Multi-core Operating Systems. Computer Science [cs]. Sor- bonne Université, 2020. English. tel-02977242 HAL Id: tel-02977242 https://hal.archives-ouvertes.fr/tel-02977242 Submitted on 24 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Ph.D thesis in Computer Science Thread Scheduling in Multi-core Operating Systems How to Understand, Improve and Fix your Scheduler Redha GOUICEM Sorbonne Université Laboratoire d’Informatique de Paris 6 Inria Whisper Team PH.D.DEFENSE: 23 October 2020, Paris, France JURYMEMBERS: Mr. Pascal Felber, Full Professor, Université de Neuchâtel Reviewer Mr. Vivien Quéma, Full Professor, Grenoble INP (ENSIMAG) Reviewer Mr. Rachid Guerraoui, Full Professor, École Polytechnique Fédérale de Lausanne Examiner Ms. Karine Heydemann, Associate Professor, Sorbonne Université Examiner Mr. Etienne Rivière, Full Professor, University of Louvain Examiner Mr. Gilles Muller, Senior Research Scientist, Inria Advisor Mr. Julien Sopena, Associate Professor, Sorbonne Université Advisor ABSTRACT In this thesis, we address the problem of schedulers for multi-core architectures from several perspectives: design (simplicity and correct- ness), performance improvement and the development of application- specific schedulers.
    [Show full text]
  • Linux CPU Schedulers: CFS and Muqss Comparison
    Umeå University 2021-06-14 Bachelor’s Thesis In Computing Science Linux CPU Schedulers: CFS and MuQSS Comparison Name David Shakoori Gustafsson Supervisor Anna Jonsson Examinator Ola Ringdahl CFS and MuQSS Comparison Abstract The goal of this thesis is to compare two process schedulers for the Linux operating system. In order to provide a responsive and interactive user ex- perience, an efficient process scheduling algorithm is important. This thesis seeks to explain the potential performance differences by analysing the sched- ulers’ respective designs. The two schedulers that are tested and compared are Con Kolivas’s MuQSS and Linux’s default scheduler, CFS. They are tested with respect to three main aspects: latency, turn-around time and interactivity. Latency is tested by using benchmarking software, the turn- around time by timing software compilation, and interactivity by measuring video frame drop percentages under various background loads. These tests are performed on a desktop PC running Linux OpenSUSE Leap 15.2, using kernel version 5.11.18. The test results show that CFS manages to keep a generally lower latency, while turn-around times differs little between the two. Running the turn-around time test’s compilation using a single process gives MuQSS a small advantage, while dividing the compilation evenly among the available logical cores yields little difference. However, CFS clearly outper- forms MuQSS in the interactivity test, where it manages to keep frame drop percentages considerably lower under each tested background load. As is apparent by the results, Linux’s current default scheduler provides a more responsive and interactive experience within the testing conditions, than the alternative MuQSS.
    [Show full text]
  • Cross-Layer Resource Control and Scheduling for Improving Interactivity in Android
    SOFTWARE—PRACTICE AND EXPERIENCE Softw. Pract. Exper. 2014; 00:1–22 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/spe Cross-Layer Resource Control and Scheduling for Improving Interactivity in Android ∗ † Sungju Huh1, Jonghun Yoo2 and Seongsoo Hong1,2,3, , 1Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Suwon-si, Gyeonggi-do, Republic of Korea 2Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea 3Advanced Institutes of Convergence Technology, Suwon-si, Gyeonggi-do, Republic of Korea SUMMARY Android smartphones are often reported to suffer from sluggish user interactions due to poor interactivity. This is partly because Android and its task scheduler, the completely fair scheduler (CFS), may incur perceptibly long response time to user-interactive tasks. Particularly, the Android framework cannot systemically favor user-interactive tasks over other background tasks since it does not distinguish between them. Furthermore, user-interactive tasks can suffer from high dispatch latency due to the non-preemptive nature of CFS. To address these problems, this paper presents framework-assisted task characterization and virtual time-based CFS. The former is a cross-layer resource control mechanism between the Android framework and the underlying Linux kernel. It identifies user-interactive tasks at the framework-level, by using the notion of a user-interactive task chain. It then enables the kernel scheduler to selectively promote the priorities of worker tasks appearing in the task chain to reduce the preemption latency. The latter is a cross-layer refinement of CFS in terms of interactivity. It allows a task to be preempted at every predefined period.
    [Show full text]
  • Abkürzungs-Liste ABKLEX
    Abkürzungs-Liste ABKLEX (Informatik, Telekommunikation) W. Alex 1. Juli 2021 Karlsruhe Copyright W. Alex, Karlsruhe, 1994 – 2018. Die Liste darf unentgeltlich benutzt und weitergegeben werden. The list may be used or copied free of any charge. Original Point of Distribution: http://www.abklex.de/abklex/ An authorized Czechian version is published on: http://www.sochorek.cz/archiv/slovniky/abklex.htm Author’s Email address: [email protected] 2 Kapitel 1 Abkürzungen Gehen wir von 30 Zeichen aus, aus denen Abkürzungen gebildet werden, und nehmen wir eine größte Länge von 5 Zeichen an, so lassen sich 25.137.930 verschiedene Abkür- zungen bilden (Kombinationen mit Wiederholung und Berücksichtigung der Reihenfol- ge). Es folgt eine Auswahl von rund 16000 Abkürzungen aus den Bereichen Informatik und Telekommunikation. Die Abkürzungen werden hier durchgehend groß geschrieben, Akzente, Bindestriche und dergleichen wurden weggelassen. Einige Abkürzungen sind geschützte Namen; diese sind nicht gekennzeichnet. Die Liste beschreibt nur den Ge- brauch, sie legt nicht eine Definition fest. 100GE 100 GBit/s Ethernet 16CIF 16 times Common Intermediate Format (Picture Format) 16QAM 16-state Quadrature Amplitude Modulation 1GFC 1 Gigabaud Fiber Channel (2, 4, 8, 10, 20GFC) 1GL 1st Generation Language (Maschinencode) 1TBS One True Brace Style (C) 1TR6 (ISDN-Protokoll D-Kanal, national) 247 24/7: 24 hours per day, 7 days per week 2D 2-dimensional 2FA Zwei-Faktor-Authentifizierung 2GL 2nd Generation Language (Assembler) 2L8 Too Late (Slang) 2MS Strukturierte
    [Show full text]
  • © Groupe Eyrolles, 2012, ISBN : 978-2-212-13382-0 Avant-Propos
    © Groupe Eyrolles, 2012, ISBN : 978-2-212-13382-0 Avant-propos La mise au point d’un système temps réel, construit sur des solutions logicielles libres peut sem- bler a priori assez compliquée. Quel noyau choisir ? Quelle version ? Faut-il ajouter des extensions ? Quelles sont les per- formances que l’on peut en espérer ? Quel sera le comportement du système en cas de pics de charge logicielle ? De charge d’interruption ? Toutes ces questions – qui se poseront à un moment ou un autre – peuvent décourager l’architecte système face à la multitude d’offres libres ou commerciales se réclamant de « Linux temps réel ». Dans ce livre, j’ai souhaité aider le concepteur, le chef de projet, le développeur, à bien saisir les éléments à prendre en considération lors de la mise au point d’un système où les performances d’ordonnancement et les temps de réponse aux interruptions sont importants. Le propos s’articu- lera donc sur le fonctionnement et les possibilités temps réel de Linux et de ses extensions libres. Nous n’aborderons ni les spécificités des distributions Linux (Ubuntu, Debian, Fedora, etc.) qui encadrent le noyau standard, ni les solutions commerciales (comme Suse Linux Enterprise Real Time, ou Red Hat Enterprise MRG) construites autour de Linux et de ses extensions temps réel auxquelles elles apportent essentiellement un support technique et une validation sur des plates- formes définies. Dans un premier temps (chapitres 1 et 2), nous examinerons quelques concepts de base concer- nant le multitâche sous Linux et les interactions entre l’espace utilisateur (dans lequel les applications s’exécutent) et l’espace kernel (contenant le code du noyau proprement dit).
    [Show full text]
  • Scheduling of Real- Time Processes, Strategies and Analysis
    FYS 4220 / 9220 – 2011 / #7 Real Time and Embedded Data Systems and Computing Scheduling of Real- Time processes, strategies and analysis T.B. Skaali, Department of Physics, University of Oslo) Some definitions to start with • The scheduler is the component of the kernel that selects which process to run next. The scheduler (or process scheduler, as it is sometimes called) can be viewed as the code that divides the finite resource of processor time between the runnable processes on a system. • Multitasking operating systems come in two flavors: cooperative multitasking and preemptive multitasking. Linux, like all Unix variants and most modern operating systems, provides preemptive multitasking. In preemptive multitasking, the scheduler decides when a process is to cease running and a new process is to resume running. The act of involuntarily suspending a running process is called preemption. The time a process runs before it is preempted is predetermined, and is called the timeslice of the process. The timeslice, in effect, gives each process a slice of the processor's time. Managing the timeslice enables the scheduler to make global scheduling decisions for the system. It also prevents any one process from monopolizing the system – Conversely, in cooperative multitasking, a process does not stop running until it voluntary decides to do so. This approach has many shortcomings T.B. Skaali, Department of Physics, University of Oslo FYS 4220/9220 - 2011 - Lecture #7 2 The challenge of scheduling in Real-Time systems • Scheduling is the problem of assigning a set of processes (tasks) to a set of resources subject to a set of constraints.
    [Show full text]
  • A Complete Guide to Linux Process Scheduling
    A complete guide to Linux process scheduling Nikita Ishkov University of Tampere School of Information Sciences Computer Science M.Sc. Thesis Supervisor: Martti Juhola February 2015 University of Tampere School of Information Sciences Computer Science Nikita Ishkov M.Sc. Thesis, 59 pages February 2015 The subject of this thesis is process scheduling in wide purpose operating systems. For many years kernel hackers all over the world tried to accomplish the seemingly infeasible task of achieving good interaction on desktop systems and low latencies on heavily loaded server machines. Some progress has been made in this area since the rise of free software, but, in opinion of many, it is still far from perfect. Lots of beginner operating system enthusiasts find the existing solutions too complex to understand and, in light of almost complete lack of documentation along with common hostility of active kernel developers towards rookies, impossible to get hands on. Anyone who has the courage to wade into the dragon infested layer that is the scheduler, should be aware of the ideas behind current implementations before making any contributions. That is what this thesis is about – showing how things work under the hood and how they developed to be like this. Every decision behind each concept in a kernel of an OS has its history and meaning. Here I will guide you through process scheduling mechanisms in currently stable Linux kernel as an object lesson on the matter. The work starts with an overview of the essentials of process abstraction in Linux, and continues with detailed code-level description of scheduling techniques involved in past and present kernels.
    [Show full text]
  • ESW08-Scheduling, Interrupt
    Rights to copy • © Copyright 2004-2019, Bootlin • License: Creative Commons Attribution - Share Alike 3.0 • https://creativecommons.org/licenses/by-sa/3.0/legalcode • You are free: – to copy, distribute, display, and perform the work – to make derivative works – to make commercial use of the work • Under the following conditions: – Attribution. You must give the original author credit. – Share Alike. If you alter, transform, or build upon this work, you may distribute the resulting work only • under a license identical to this one. – For any reuse or distribution, you must make clear to others the license terms of this work. – Any of these conditions can be waived if you get permission from the copyright holder. • Your fair use and other rights are in no way affected by the above. • Document sources: https://git.bootlin.com/training-materials/ Dongkun Shin, SKKU 1 8. Task scheduling Dongkun Shin, SKKU 2 Process, thread? • Confusion about the terms process, thread and task • A process is created using fork() and is composed of – An address space, which contains the program code, data, stack, shared libraries, etc. – One thread, that starts executing the main() function. – Upon creation, a process contains one thread • Additional threads can be created inside an existing process, using pthread_create() – They run in the same address space as the initial thread of the process – They start executing a function passed as argument to pthread_create() • The kernel represents each thread running in the system by a structure of type struct task_struct • From a scheduling point of view, it makes no difference between the initial thread of a process and all additional threads created dynamically using pthread_create() Dongkun Shin, SKKU 3 A thread life Dongkun Shin, SKKU 4 Execution of system calls Dongkun Shin, SKKU 5 Task Schedulers and Load Balancing • The OS scheduler assigns tasks to cores by assessing a number of parameters, such as task priority, how much time the task has had, and how long it was since last run.
    [Show full text]
  • Computer Programming and Cyber Security for Beginners
    Computer Programming and Cyber Security for Beginners This Book Includes : Python Machine Learning , SQL , Linux , Hacking with Kali Linux , Ethical Hacking . Coding and Cybersecurity Fundamentals Zach Codings Download the Audio Book Version of This Book for FREE If you love listening to audio books on-the-go, I have great news for you. You can download the audio book version of this book for FREE just by signing up for a FREE 30-day audible trial! See below for more details! Audible Trial Benefits As an audible customer, you will receive the below benefits with your 30- day free trial: FREE audible book copy of this book After the trial, you will get 1 credit each month to use on any audiobook Your credits automatically roll over to the next month if you don’t use them Choose from Audible’s 200,000 + titles Listen anywhere with the Audible app across multiple devices Make easy, no-hassle exchanges of any audiobook you don’t love Keep your audiobooks forever, even if you cancel your membership And much more Click the links below to get started! For Audible US For Audible UK For Audible FR For Audible DE © Copyright 2019 by Zach Codings All rights reserved. The content contained within this book may not be reproduced, duplicated or transmitted without direct written permission from the author or the publisher. Under no circumstances will any blame or legal responsibility be held against the publisher, or author, for any damages, reparation, or monetary loss due to the information contained within this book, either directly or indirectly.
    [Show full text]
  • Free for All How Linux and the Free Software Move- Ment Undercut the High-Tech Titans
    Free for All How Linux and the Free Software Move- ment Undercut the High-Tech Titans by Peter Wayner This is the free electronic version of the book originally published by HarperCollins. The book is still protected by copyright and bound by a license granting you the limited rights to make complete copies for non-commercial purposes.You’re welcome to read it in electronic form subject to these conditions: 1) You may not make derivative works. You must reproduce the work in its entirety. 2) You may not sell versions. 3) You refer everyone receiving a copy to the website where they may get the latest corrected version. (http://www.wayner.org/books/ffa/). A full license developed by the Creative Commons (www.creativecommons.org) will be forth- coming. Please write ([email protected]) if you have any questions or suggestions. Disappearing Cryptography, 2nd Edition Information Hiding: Steganography & Watermarking by Peter Wayner ISBN 1-55860-769-2 $44.95 To order, visit: http://www.wayner.org/books/discrypt2/ Disappearing Cryptography, Second Edition describes how to take words, sounds, or images and hide them in digital data so they look like other words, sounds, or images. When used properly, this powerful technique makes it almost impossible to trace the author and the recipient of a message. Conversations can be sub- merged in the flow of information through the Internet so that no one can know if a conversation exists at all. This full revision of the best-selling first edition “Disappearing Cryptography is a witty and enter- describes a number of different techniques to hide taining look at the world of information hiding.
    [Show full text]