Understanding the Impact of Cache Locations on Storage Performance and Energy Consumption of Virtualization Systems
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The Linux Kernel Module Programming Guide
The Linux Kernel Module Programming Guide Peter Jay Salzman Michael Burian Ori Pomerantz Copyright © 2001 Peter Jay Salzman 2007−05−18 ver 2.6.4 The Linux Kernel Module Programming Guide is a free book; you may reproduce and/or modify it under the terms of the Open Software License, version 1.1. You can obtain a copy of this license at http://opensource.org/licenses/osl.php. This book is distributed in the hope it will be useful, but without any warranty, without even the implied warranty of merchantability or fitness for a particular purpose. The author encourages wide distribution of this book for personal or commercial use, provided the above copyright notice remains intact and the method adheres to the provisions of the Open Software License. In summary, you may copy and distribute this book free of charge or for a profit. No explicit permission is required from the author for reproduction of this book in any medium, physical or electronic. Derivative works and translations of this document must be placed under the Open Software License, and the original copyright notice must remain intact. If you have contributed new material to this book, you must make the material and source code available for your revisions. Please make revisions and updates available directly to the document maintainer, Peter Jay Salzman <[email protected]>. This will allow for the merging of updates and provide consistent revisions to the Linux community. If you publish or distribute this book commercially, donations, royalties, and/or printed copies are greatly appreciated by the author and the Linux Documentation Project (LDP). -
Interrupt Handling in Linux
Department Informatik Technical Reports / ISSN 2191-5008 Valentin Rothberg Interrupt Handling in Linux Technical Report CS-2015-07 November 2015 Please cite as: Valentin Rothberg, “Interrupt Handling in Linux,” Friedrich-Alexander-Universitat¨ Erlangen-Nurnberg,¨ Dept. of Computer Science, Technical Reports, CS-2015-07, November 2015. Friedrich-Alexander-Universitat¨ Erlangen-Nurnberg¨ Department Informatik Martensstr. 3 · 91058 Erlangen · Germany www.cs.fau.de Interrupt Handling in Linux Valentin Rothberg Distributed Systems and Operating Systems Dept. of Computer Science, University of Erlangen, Germany [email protected] November 8, 2015 An interrupt is an event that alters the sequence of instructions executed by a processor and requires immediate attention. When the processor receives an interrupt signal, it may temporarily switch control to an inter- rupt service routine (ISR) and the suspended process (i.e., the previously running program) will be resumed as soon as the interrupt is being served. The generic term interrupt is oftentimes used synonymously for two terms, interrupts and exceptions [2]. An exception is a synchronous event that occurs when the processor detects an error condition while executing an instruction. Such an error condition may be a devision by zero, a page fault, a protection violation, etc. An interrupt, on the other hand, is an asynchronous event that occurs at random times during execution of a pro- gram in response to a signal from hardware. A proper and timely handling of interrupts is critical to the performance, but also to the security of a computer system. In general, interrupts can be emitted by hardware as well as by software. Software interrupts (e.g., via the INT n instruction of the x86 instruction set architecture (ISA) [5]) are means to change the execution context of a program to a more privileged interrupt context in order to enter the kernel and, in contrast to hardware interrupts, occur synchronously to the currently running program. -
Linux: Kernel Release Number, Part II
Linux: Kernel Release Number, Part II Posted by jeremy on Friday, March 4, 2005 - 07:05 In the continued discussion on release numbering for the Linux kernel [story], Linux creator Linus Torvalds decided against trying to add meaning to the odd/even least significant number. Instead, the new plan is to go from the current 2.6.x numbering to a finer-grained 2.6.x.y. Linus will continue to maintain only the 2.6.x releases, and the -rc releases in between. Others will add trivial patches to create the 2.6.x.y releases. Linus cautions that the task of maintaining a 2.6.x.y tree is not going to be enjoyable: "I'll tell you what the problem is: I don't think you'll find anybody to do the parallell 'only trivial patches' tree. They'll go crazy in a couple of weeks. Why? Because it's a _damn_ hard problem. Where do you draw the line? What's an acceptable patch? And if you get it wrong, people will complain _very_ loudly, since by now you've 'promised' them a kernel that is better than the mainline. In other words: there's almost zero glory, there are no interesting problems, and there will absolutely be people who claim that you're a dick-head and worse, probably on a weekly basis." He went on to add, "that said, I think in theory it's a great idea. It might even be technically feasible if there was some hard technical criteria for each patch that gets accepted, so that you don't have the burn-out problem." His suggested criteria included limiting the patch to being 100 lines or less, and requiring that it fix an oops, a hang, or an exploitable security hole. -
Open Source Software Notice
OPEN SOURCE SOFTWARE NOTICE DCS Touch Display Software V2.00.XXX Schüco International KG Karolinenstraße 1-15 33609 Bielefeld OPEN SOURCE SOFTWARE NOTICE Seite 1 von 32 10000507685_02_EN OPEN SOURCE SOFTWARE NOTICE This document contains information about open source software for this product. The rights granted under open source software licenses are granted by the respective right holders. In the event of conflicts between SCHÜCO’S license conditions and the applicable open source licenses, the open source license conditions take precedence over SCHÜCO’S license conditions with regard to the respective open source software. You are allowed to modify SCHÜCO’S proprietary programs and to conduct reverse engineering for the purpose of debugging such modifications, to the extent such programs are linked to libraries licensed under the GNU Lesser General Public License. You are not allowed to distribute information resulting from such reverse engineering or to distribute the modified proprietary programs. The rightholders of the open source software require to refer to the following disclaimer, which shall apply with regard to those rightholders: Warranty Disclaimer THE OPEN SOURCE SOFTWARE IN THIS PRODUCT IS DISTRIBUTED ON AN "AS IS" BASIS AND IN THE HOPE THAT IT WILL BE USEFUL, BUT WITHOUT ANY WARRANTY OF ANY KIND, WITHOUT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. SEE THE APPLICABLE LICENSES FOR MORE DETAILS. OPEN SOURCE SOFTWARE NOTICE Seite 2 von 32 10000507685_02_EN Copyright Notices and License Texts (please see the source code for all details) Software: iptables Copyright notice: Copyright (C) 1989, 1991 Free Software Foundation, Inc. Copyright Google, Inc. -
16-Bit MS-DOS Programming (MS-DOS & BIOS-Level Programming )
Microprocessors (0630371) Fall 2010/2011 – Lecture Notes # 20 16-Bit MS-DOS Programming (MS-DOS & BIOS-level Programming ) Objectives Real-Address Mode MS-DOS Memory Organization MS-DOS Memory Map Interrupts Mechanism—Introduction Interrupts Mechanism — Steps Types of Interrupts 8086/8088 Pinout Diagrams Redirecting Input-Output INT Instruction Interrupt Vectoring Process Common Interrupts Real-Address Mode Real-address mode (16-bit mode) programs have the following characteristics: o Max 1 megabyte addressable RAM o Single tasking o No memory boundary protection o Offsets are 16 bits IBM PC-DOS: first Real-address OS for IBM-PC Later renamed to MS-DOS, owned by Microsoft MS-DOS Memory Organization Interrupt Vector Table BIOS & DOS data Software BIOS MS-DOS kernel Resident command processor Transient programs Video graphics & text Reserved (device controllers) ROM BIOS MS-DOS Memory Map Address FFFFF R O M BIO S F0000 Reserved C0000 Video Text & Graphics B8000 V R A M Video Graphics A0000 Transient Command Processor Transient Program Area (available for application programs) Resident Command Processor 640K R A M DOS Kernel, Device Drivers Software BIOS BIOS & DOS Data 00400 Interrupt Vector Table 00000 Interrupt Mechanism—Introduction Devices such as the keyboard, the monitor, hard disks etc. can cause such interrupts, when they require service of some kind, such as to get or receive a byte. For example, when you press a key on the keyboard this causes an interrupt. When the Microprocessor is interrupted, it completes the current instruction, and then pushes onto the stack the flags register plus the address of the next instruction (the return address). -
The Xen Port of Kexec / Kdump a Short Introduction and Status Report
The Xen Port of Kexec / Kdump A short introduction and status report Magnus Damm Simon Horman VA Linux Systems Japan K.K. www.valinux.co.jp/en/ Xen Summit, September 2006 Magnus Damm ([email protected]) Kexec / Kdump Xen Summit, September 2006 1 / 17 Outline Introduction to Kexec What is Kexec? Kexec Examples Kexec Overview Introduction to Kdump What is Kdump? Kdump Kernels The Crash Utility Xen Porting Effort Kexec under Xen Kdump under Xen The Dumpread Tool Partial Dumps Current Status Magnus Damm ([email protected]) Kexec / Kdump Xen Summit, September 2006 2 / 17 Introduction to Kexec Outline Introduction to Kexec What is Kexec? Kexec Examples Kexec Overview Introduction to Kdump What is Kdump? Kdump Kernels The Crash Utility Xen Porting Effort Kexec under Xen Kdump under Xen The Dumpread Tool Partial Dumps Current Status Magnus Damm ([email protected]) Kexec / Kdump Xen Summit, September 2006 3 / 17 Kexec allows you to reboot from Linux into any kernel. as long as the new kernel doesn’t depend on the BIOS for setup. Introduction to Kexec What is Kexec? What is Kexec? “kexec is a system call that implements the ability to shutdown your current kernel, and to start another kernel. It is like a reboot but it is indepedent of the system firmware...” Configuration help text in Linux-2.6.17 Magnus Damm ([email protected]) Kexec / Kdump Xen Summit, September 2006 4 / 17 . as long as the new kernel doesn’t depend on the BIOS for setup. Introduction to Kexec What is Kexec? What is Kexec? “kexec is a system call that implements the ability to shutdown your current kernel, and to start another kernel. -
Kernel Boot-Time Tracing
Kernel Boot-time Tracing Linux Plumbers Conference 2019 - Tracing Track Masami Hiramatsu <[email protected]> Linaro, Ltd. Speaker Masami Hiramatsu - Working for Linaro and Linaro members - Tech Lead for a Landing team - Maintainer of Kprobes and related tracing features/tools Why Kernel Boot-time Tracing? Debug and analyze boot time errors and performance issues - Measure performance statistics of kernel boot - Analyze driver init failure - Debug boot up process - Continuously tracing from boot time etc. What We Have There are already many ftrace options on kernel command line ● Setup options (trace_options=) ● Output to printk (tp_printk) ● Enable events (trace_events=) ● Enable tracers (ftrace=) ● Filtering (ftrace_filter=,ftrace_notrace=,ftrace_graph_filter=,ftrace_graph_notrace=) ● Add kprobe events (kprobe_events=) ● And other options (alloc_snapshot, traceoff_on_warning, ...) See Documentation/admin-guide/kernel-parameters.txt Example of Kernel Cmdline Parameters In grub.conf linux /boot/vmlinuz-5.1 root=UUID=5a026bbb-6a58-4c23-9814-5b1c99b82338 ro quiet splash tp_printk trace_options=”sym-addr” trace_clock=global ftrace_dump_on_oops trace_buf_size=1M trace_event=”initcall:*,irq:*,exceptions:*” kprobe_event=”p:kprobes/myevent foofunction $arg1 $arg2;p:kprobes/myevent2 barfunction %ax” What Issues? Size limitation ● kernel cmdline size is small (< 256bytes) ● A half of the cmdline is used for normal boot Only partial features supported ● ftrace has too complex features for single command line ● per-event filters/actions, instances, histograms. Solutions? 1. Use initramfs - Too late for kernel boot time tracing 2. Expand kernel cmdline - It is not easy to write down complex tracing options on bootloader (Single line options is too simple) 3. Reuse structured boot time data (Devicetree) - Well documented, structured data -> V1 & V2 series based on this. Boot-time Trace: V1 and V2 series V1 and V2 series posted at June. -
Anatomy of Linux Loadable Kernel Modules a 2.6 Kernel Perspective
Anatomy of Linux loadable kernel modules A 2.6 kernel perspective Skill Level: Intermediate M. Tim Jones ([email protected]) Consultant Engineer Emulex Corp. 16 Jul 2008 Linux® loadable kernel modules, introduced in version 1.2 of the kernel, are one of the most important innovations in the Linux kernel. They provide a kernel that is both scalable and dynamic. Discover the ideas behind loadable modules, and learn how these independent objects dynamically become part of the Linux kernel. The Linux kernel is what's known as a monolithic kernel, which means that the majority of the operating system functionality is called the kernel and runs in a privileged mode. This differs from a micro-kernel, which runs only basic functionality as the kernel (inter-process communication [IPC], scheduling, basic input/output [I/O], memory management) and pushes other functionality outside the privileged space (drivers, network stack, file systems). You'd think that Linux is then a very static kernel, but in fact it's quite the opposite. Linux can be dynamically altered at run time through the use of Linux kernel modules (LKMs). More in Tim's Anatomy of... series on developerWorks • Anatomy of Linux flash file systems • Anatomy of Security-Enhanced Linux (SELinux) • Anatomy of real-time Linux architectures • Anatomy of the Linux SCSI subsystem • Anatomy of the Linux file system • Anatomy of the Linux networking stack Anatomy of Linux loadable kernel modules © Copyright IBM Corporation 1994, 2008. All rights reserved. Page 1 of 11 developerWorks® ibm.com/developerWorks • Anatomy of the Linux kernel • Anatomy of the Linux slab allocator • Anatomy of Linux synchronization methods • All of Tim's Anatomy of.. -
Linux Perf Event Features and Overhead
Linux perf event Features and Overhead 2013 FastPath Workshop Vince Weaver http://www.eece.maine.edu/∼vweaver [email protected] 21 April 2013 Performance Counters and Workload Optimized Systems • With processor speeds constant, cannot depend on Moore's Law to deliver increased performance • Code analysis and optimization can provide speedups in existing code on existing hardware • Systems with a single workload are best target for cross- stack hardware/kernel/application optimization • Hardware performance counters are the perfect tool for this type of optimization 1 Some Uses of Performance Counters • Traditional analysis and optimization • Finding architectural reasons for slowdown • Validating Simulators • Auto-tuning • Operating System optimization • Estimating power/energy in software 2 Linux and Performance Counters • Linux has become the operating system of choice in many domains • Runs most of the Top500 list (over 90%) on down to embedded devices (Android Phones) • Until recently had no easy access to hardware performance counters, limiting code analysis and optimization. 3 Linux Performance Counter History • oprofile { system-wide sampling profiler since 2002 • perfctr { widely used general interface available since 1999, required patching kernel • perfmon2 { another general interface, included in kernel for itanium, made generic, big push for kernel inclusion 4 Linux perf event • Developed in response to perfmon2 by Molnar and Gleixner in 2009 • Merged in 2.6.31 as \PCL" • Unusual design pushes most functionality into kernel -
Lesson-2: Interrupt and Interrupt Service Routine Concept
DEVICE DRIVERS AND INTERRUPTS SERVICE MECHANISM Lesson-2: Interrupt and Interrupt Service Routine Concept Chapter 6 L2: "Embedded Systems- Architecture, Programming and Design", 2015 1 Raj Kamal, Publs.: McGraw-Hill Education Interrupt Concept • Interrupt means event, which invites attention of the processor on occurrence of some action at hardware or software interrupt instruction event. Chapter 6 L2: "Embedded Systems- Architecture, Programming and Design", 2015 2 Raj Kamal, Publs.: McGraw-Hill Education Action on Interrupt In response to the interrupt, a routine or program (called foreground program), which is running presently interrupts and an interrupt service routine (ISR) executes. Chapter 6 L2: "Embedded Systems- Architecture, Programming and Design", 2015 3 Raj Kamal, Publs.: McGraw-Hill Education Interrupt Service Routine ISR is also called device driver in case of the devices and called exception or signal or trap handler in case of software interrupts Chapter 6 L2: "Embedded Systems- Architecture, Programming and Design", 2015 4 Raj Kamal, Publs.: McGraw-Hill Education Interrupt approach for the port or device functions Processor executes the program, called interrupt service routine or signal handler or trap handler or exception handler or device driver, related to input or output from the port or device or related to a device function on an interrupt and does not wait and look for the input ready or output completion or device-status ready or set Chapter 6 L2: "Embedded Systems- Architecture, Programming and Design", -
Additional Functions in HW-RTOS Offering the Low Interrupt Latency
HW-RTOS Real Time OS in Hardware Additional Functions in HW-RTOS Offering the Low Interrupt Latency In this white paper, we introduce two HW-RTOS functions that offer the lowest interrupt latency available and help create a more software-friendly environment. One of these is ISR implemented in hardware, which improves responsiveness when activating a task from an interrupt and eliminates the need for developing a handler in software. The other is a function allowing the use of non-OS managed interrupt handlers in a multitasking environment. This makes it easier to migrate from a non-RTOS environment to a multitasking one. R70WP0003EJ0100 September, 2018 2 / 8 Multitasking Environment with Lowest Interrupt Latency Offered by HW-RTOS 1. Executive Summary In this white paper, we introduce two functions special to HW-RTOS that improve interrupt performance. The first is the HW ISR function. Renesas stylized the ISR (Interrupt Service Routine) process and implemented it in hardware to create their HW ISR. With this function, the task corresponding to the interrupt signal can be activated directly and in real time. And, since the ISR is implemented in the hardware, application software engineers are relieved of the burden of developing a handler. The second is called Direct Interrupt Service. This function is equivalent to allowing a non-OS managed interrupt handler to invoke an API. This function %" "$# $""%!$ $ $""%!$!" enables synchronization and communication "$ "$ between the non-OS managed interrupt handler and $($ $($ '$ '$ tasks, a benefit not available in conventional $ $ software. In other words, it allows the use of non-OS # $ % " "$) ) managed interrupt handlers in a multitasking $($ '$ environment. -
Exceptions and Processes
Exceptions and Processes! Jennifer Rexford! The material for this lecture is drawn from! Computer Systems: A Programmerʼs Perspective (Bryant & O"Hallaron) Chapter 8! 1 Goals of this Lecture! •#Help you learn about:! •# Exceptions! •# The process concept! … and thereby…! •# How operating systems work! •# How applications interact with OS and hardware! The process concept is one of the most important concepts in systems programming! 2 Context of this Lecture! Second half of the course! Previously! Starting Now! C Language! Application Program! language! service! levels! Assembly Language! levels! Operating System! tour! tour! Machine Language! Hardware! Application programs, OS,! and hardware interact! via exceptions! 3 Motivation! Question:! •# How does a program get input from the keyboard?! •# How does a program get data from a (slow) disk?! Question:! •# Executing program thinks it has exclusive control of CPU! •# But multiple programs share one CPU (or a few CPUs)! •# How is that illusion implemented?! Question:! •# Executing program thinks it has exclusive use of memory! •# But multiple programs must share one memory! •# How is that illusion implemented?! Answers: Exceptions…! 4 Exceptions! •# Exception! •# An abrupt change in control flow in response to a change in processor state! •# Examples:! •# Application program:! •# Requests I/O! •# Requests more heap memory! •# Attempts integer division by 0! •# Attempts to access privileged memory! Synchronous! •# Accesses variable that is not$ in real memory (see upcoming $ “Virtual Memory” lecture)! •# User presses key on keyboard! Asynchronous! •# Disk controller finishes reading data! 5 Exceptions Note! •# Note:! ! !Exceptions in OS % exceptions in Java! Implemented using! try/catch! and throw statements! 6 Exceptional Control Flow! Application! Exception handler! program! in operating system! exception! exception! processing! exception! return! (optional)! 7 Exceptions vs.