Use of Seek When Writing Or Reading Binary Files
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Copy on Write Based File Systems Performance Analysis and Implementation
Copy On Write Based File Systems Performance Analysis And Implementation Sakis Kasampalis Kongens Lyngby 2010 IMM-MSC-2010-63 Technical University of Denmark Department Of Informatics Building 321, DK-2800 Kongens Lyngby, Denmark Phone +45 45253351, Fax +45 45882673 [email protected] www.imm.dtu.dk Abstract In this work I am focusing on Copy On Write based file systems. Copy On Write is used on modern file systems for providing (1) metadata and data consistency using transactional semantics, (2) cheap and instant backups using snapshots and clones. This thesis is divided into two main parts. The first part focuses on the design and performance of Copy On Write based file systems. Recent efforts aiming at creating a Copy On Write based file system are ZFS, Btrfs, ext3cow, Hammer, and LLFS. My work focuses only on ZFS and Btrfs, since they support the most advanced features. The main goals of ZFS and Btrfs are to offer a scalable, fault tolerant, and easy to administrate file system. I evaluate the performance and scalability of ZFS and Btrfs. The evaluation includes studying their design and testing their performance and scalability against a set of recommended file system benchmarks. Most computers are already based on multi-core and multiple processor architec- tures. Because of that, the need for using concurrent programming models has increased. Transactions can be very helpful for supporting concurrent program- ming models, which ensure that system updates are consistent. Unfortunately, the majority of operating systems and file systems either do not support trans- actions at all, or they simply do not expose them to the users. -
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). -
File Storage Techniques in Labview
File Storage Techniques in LabVIEW Starting with a set of data as if it were generated by a daq card reading two channels and 10 samples per channel, we end up with the following array: Note that the first radix is the channel increment, and the second radix is the sample number. We will use this data set for all the following examples. The first option is to send it directly to a spreadsheet file. spreadsheet save of 2D data.png The data is wired to the 2D array input and all the defaults are taken. This will ask for a file name when the program block is run, and create a file with data values, separated by tab characters, as follows: 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000 9.000 10.000 10.000 20.000 30.000 40.000 50.000 60.000 70.000 80.000 90.000 100.000 Note that each value is in the format x.yyy, with the y's being zeros. The default format for the write to spreadsheet VI is "%.3f" which will generate a floating point number with 3 decimal places. If a number with higher decimal places is entered in the array, it would be truncated to three. Since the data file is created in row format, and what you really need if you are going to import it into excel, is column format. There are two ways to resolve this, the first is to set the transpose bit on the write function, and the second, is to add an array transpose, located in the array pallet. -
System Calls System Calls
System calls We will investigate several issues related to system calls. Read chapter 12 of the book Linux system call categories file management process management error handling note that these categories are loosely defined and much is behind included, e.g. communication. Why? 1 System calls File management system call hierarchy you may not see some topics as part of “file management”, e.g., sockets 2 System calls Process management system call hierarchy 3 System calls Error handling hierarchy 4 Error Handling Anything can fail! System calls are no exception Try to read a file that does not exist! Error number: errno every process contains a global variable errno errno is set to 0 when process is created when error occurs errno is set to a specific code associated with the error cause trying to open file that does not exist sets errno to 2 5 Error Handling error constants are defined in errno.h here are the first few of errno.h on OS X 10.6.4 #define EPERM 1 /* Operation not permitted */ #define ENOENT 2 /* No such file or directory */ #define ESRCH 3 /* No such process */ #define EINTR 4 /* Interrupted system call */ #define EIO 5 /* Input/output error */ #define ENXIO 6 /* Device not configured */ #define E2BIG 7 /* Argument list too long */ #define ENOEXEC 8 /* Exec format error */ #define EBADF 9 /* Bad file descriptor */ #define ECHILD 10 /* No child processes */ #define EDEADLK 11 /* Resource deadlock avoided */ 6 Error Handling common mistake for displaying errno from Linux errno man page: 7 Error Handling Description of the perror () system call. -
Ext4 File System and Crash Consistency
1 Ext4 file system and crash consistency Changwoo Min 2 Summary of last lectures • Tools: building, exploring, and debugging Linux kernel • Core kernel infrastructure • Process management & scheduling • Interrupt & interrupt handler • Kernel synchronization • Memory management • Virtual file system • Page cache and page fault 3 Today: ext4 file system and crash consistency • File system in Linux kernel • Design considerations of a file system • History of file system • On-disk structure of Ext4 • File operations • Crash consistency 4 File system in Linux kernel User space application (ex: cp) User-space Syscalls: open, read, write, etc. Kernel-space VFS: Virtual File System Filesystems ext4 FAT32 JFFS2 Block layer Hardware Embedded Hard disk USB drive flash 5 What is a file system fundamentally? int main(int argc, char *argv[]) { int fd; char buffer[4096]; struct stat_buf; DIR *dir; struct dirent *entry; /* 1. Path name -> inode mapping */ fd = open("/home/lkp/hello.c" , O_RDONLY); /* 2. File offset -> disk block address mapping */ pread(fd, buffer, sizeof(buffer), 0); /* 3. File meta data operation */ fstat(fd, &stat_buf); printf("file size = %d\n", stat_buf.st_size); /* 4. Directory operation */ dir = opendir("/home"); entry = readdir(dir); printf("dir = %s\n", entry->d_name); return 0; } 6 Why do we care EXT4 file system? • Most widely-deployed file system • Default file system of major Linux distributions • File system used in Google data center • Default file system of Android kernel • Follows the traditional file system design 7 History of file system design 8 UFS (Unix File System) • The original UNIX file system • Design by Dennis Ritche and Ken Thompson (1974) • The first Linux file system (ext) and Minix FS has a similar layout 9 UFS (Unix File System) • Performance problem of UFS (and the first Linux file system) • Especially, long seek time between an inode and data block 10 FFS (Fast File System) • The file system of BSD UNIX • Designed by Marshall Kirk McKusick, et al. -
File Handling in Python
hapter C File Handling in 2 Python There are many ways of trying to understand programs. People often rely too much on one way, which is called "debugging" and consists of running a partly- understood program to see if it does what you expected. Another way, which ML advocates, is to install some means of understanding in the very programs themselves. — Robin Milner In this Chapter » Introduction to Files » Types of Files » Opening and Closing a 2.1 INTRODUCTION TO FILES Text File We have so far created programs in Python that » Writing to a Text File accept the input, manipulate it and display the » Reading from a Text File output. But that output is available only during » Setting Offsets in a File execution of the program and input is to be entered through the keyboard. This is because the » Creating and Traversing a variables used in a program have a lifetime that Text File lasts till the time the program is under execution. » The Pickle Module What if we want to store the data that were input as well as the generated output permanently so that we can reuse it later? Usually, organisations would want to permanently store information about employees, inventory, sales, etc. to avoid repetitive tasks of entering the same data. Hence, data are stored permanently on secondary storage devices for reusability. We store Python programs written in script mode with a .py extension. Each program is stored on the secondary device as a file. Likewise, the data entered, and the output can be stored permanently into a file. -
System Calls and Standard I/O
System Calls and Standard I/O Professor Jennifer Rexford http://www.cs.princeton.edu/~jrex 1 Goals of Today’s Class • System calls o How a user process contacts the Operating System o For advanced services that may require special privilege • Standard I/O library o Generic I/O support for C programs o A smart wrapper around I/O-related system calls o Stream concept, line-by-line input, formatted output, ... 2 1 System Calls 3 Communicating With the OS User Process signals systems calls Operating System • System call o Request to the operating system to perform a task o … that the process does not have permission to perform • Signal o Asynchronous notification sent to a process … to notify the process of an event that has occurred o 4 2 Processor Modes • The OS must restrict what a user process can do o What instructions can execute o What portions of the address space are accessible • Supervisor mode (or kernel mode) o Can execute any instructions in the instruction set – Including halting the processor, changing mode bit, initiating I/O o Can access any memory location in the system – Including code and data in the OS address space • User mode o Restricted capabilities – Cannot execute privileged instructions – Cannot directly reference code or data in OS address space o Any such attempt results in a fatal “protection fault” – Instead, access OS code and data indirectly via system calls 5 Main Categories of System Calls • File system o Low-level file I/O o E.g., creat, open, read, write, lseek, close • Multi-tasking mechanisms o Process -
Chapter 10 Streams Streams Text Files and Binary Files
Streams Chapter 10 • A stream is an object that enables the flow of File I/O data between a ppgrogram and some I/O device or file – If the data flows into a program, then the stream is called an input stream – If the dtdata flows out of a program, then the stream is called an output stream Copyright © 2012 Pearson Addison‐Wesley. All rights reserved. 10‐2 Streams Text Files and Binary Files • Input streams can flow from the kbkeyboar d or from a • Files that are designed to be read by human beings, file and that can be read or written with an editor are – StSystem. in is an itinput stream tha t connects to the called text files keyboard – Scanner keyy(y);board = new Scanner(System.in); Text files can also be called ASCII files because the data they contain uses an ASCII encoding scheme • Output streams can flow to a screen or to a file – An advantage of text files is that the are usually the same – System.out is an output stream that connects to the screen on all computers, so tha t they can move from one System.out.println("Output stream"); computer to another Copyright © 2012 Pearson Addison‐Wesley. All rights reserved. 10‐3 Copyright © 2012 Pearson Addison‐Wesley. All rights reserved. 10‐4 Text Files and Binary Files Writing to a Text File • Files tha t are didesigne d to be read by programs and • The class PrintWriter is a stream class that consist of a sequence of binary digits are called binary files that can be used to write to a text file – Binary files are designed to be read on the same type of – An object of the class PrintWriter has the computer and with the same programming language as the computer that created the file methods print and println – An advantage of binary files is that they are more efficient – These are similar to the System.out methods to process than text files of the same names, but are used for text file – Unlike most binary files, Java binary files have the advantage of being platform independent also output, not screen output Copyright © 2012 Pearson Addison‐Wesley. -
Automatic Porting of Binary File Descriptor Library
Automatic Porting of Binary File Descriptor Library Maghsoud Abbaspour+, Jianwen Zhu++ Technical Report TR-09-01 September 2001 + Electrical and Computer Engineering University of Tehran, Iran ++ 10 King's College Road Edward S. Rogers Sr. Electrical and Computer Engineering University of Toronto, Ontario M5S 3G4, Canada [email protected] [email protected] Abstract Since software is playing an increasingly important role in system-on-chip, retargetable compi- lation has been an active research area in the last few years. However, the retargetting of equally important downstream system tools, such as assemblers, linkers and debuggers, has either been ignored, or falls short of production quality due to the complexity involved in these tools. In this paper, we present a technique that can automatically retarget the GNU BFD library, the foundation library for a suite of binary tools. Other than having all the advantages enjoyed by open-source software by aligning to a de facto standard, our technique is systematic, as a result of using a formal model of abstract binary interface (ABI) as a new element of architectural model; and simple, as a result of leveraging free software to the largest extent. Contents 1 Introduction 1 2 Related Work 2 3 Binary File Descriptor Library (BFD) 3 4 ABI Modeling 5 5 Retargetting BFD 9 6 Implementation and Experiments 10 7 Conclusion 12 8 References 12 i 1 Introduction New products in consumer electronics and telecommunications are characterized by increasing functional complexity and shorter design cycle. It is generally conceived that the complexity problem can be best solved by the use of system-on-chip (SOC) technology. -
File and Console I/O
File and Console I/O CS449 Spring 2016 What is a Unix(or Linux) File? • File: “a resource for storing information [sic] based on some kind of durable storage” (Wikipedia) • Wider sense: “In Unix, everything is a file.” (a.k.a “In Unix, everything is a stream of bytes.”) – Traditional files, directories, links – Inter-process communication (pipes, shared memory, sockets) – Devices (interactive terminals, hard drives, printers, graphic card) • Usually mounted under /dev/ directory – Process Links (for getting process information) • Usually mounted under /proc/ directory Stream of Bytes Abstraction • A file, in abstract, is a stream of bytes • Can be manipulated using five system calls: – open: opens a file for reading/writing and returns a file descriptor • File descriptor: index into an OS array called open file table – read: reads current offset through file descriptor – write: writes current offset through file descriptor – lseek: changes current offset in file – close: closes file descriptor • Some files do not support certain operations (e.g. a terminal device does not support lseek) C Standard Library Wrappers • C Standard Library wraps file system calls in library functions – For portability across multiple systems – To provide additional features (buffering, formatting) • All C wrappers buffered by default – Buffering can be controlled using “setbuf” or “setlinebuf” calls (remember those?) • Works on FILE * instead of file descriptor – FILE is a library data structure that abstracts a file – Contains file descriptor, current offset, buffering mode etc. Wrappers for the Five System Calls Function Prototype Description FILE *fopen(const char *path, const Opens the file whose name is the string pointed to char *mode); by path and associates a stream with it. -
Filesystem Considerations for Embedded Devices ELC2015 03/25/15
Filesystem considerations for embedded devices ELC2015 03/25/15 Tristan Lelong Senior embedded software engineer Filesystem considerations ABSTRACT The goal of this presentation is to answer a question asked by several customers: which filesystem should you use within your embedded design’s eMMC/SDCard? These storage devices use a standard block interface, compatible with traditional filesystems, but constraints are not those of desktop PC environments. EXT2/3/4, BTRFS, F2FS are the first of many solutions which come to mind, but how do they all compare? Typical queries include performance, longevity, tools availability, support, and power loss robustness. This presentation will not dive into implementation details but will instead summarize provided answers with the help of various figures and meaningful test results. 2 TABLE OF CONTENTS 1. Introduction 2. Block devices 3. Available filesystems 4. Performances 5. Tools 6. Reliability 7. Conclusion Filesystem considerations ABOUT THE AUTHOR • Tristan Lelong • Embedded software engineer @ Adeneo Embedded • French, living in the Pacific northwest • Embedded software, free software, and Linux kernel enthusiast. 4 Introduction Filesystem considerations Introduction INTRODUCTION More and more embedded designs rely on smart memory chips rather than bare NAND or NOR. This presentation will start by describing: • Some context to help understand the differences between NAND and MMC • Some typical requirements found in embedded devices designs • Potential filesystems to use on MMC devices 6 Filesystem considerations Introduction INTRODUCTION Focus will then move to block filesystems. How they are supported, what feature do they advertise. To help understand how they compare, we will present some benchmarks and comparisons regarding: • Tools • Reliability • Performances 7 Block devices Filesystem considerations Block devices MMC, EMMC, SD CARD Vocabulary: • MMC: MultiMediaCard is a memory card unveiled in 1997 by SanDisk and Siemens based on NAND flash memory. -
[MS-CFB]: Compound File Binary File Format
[MS-CFB]: Compound File Binary File Format Intellectual Property Rights Notice for Open Specifications Documentation . Technical Documentation. Microsoft publishes Open Specifications documentation (“this documentation”) for protocols, file formats, data portability, computer languages, and standards support. Additionally, overview documents cover inter-protocol relationships and interactions. Copyrights. This documentation is covered by Microsoft copyrights. Regardless of any other terms that are contained in the terms of use for the Microsoft website that hosts this documentation, you can make copies of it in order to develop implementations of the technologies that are described in this documentation and can distribute portions of it in your implementations that use these technologies or in your documentation as necessary to properly document the implementation. You can also distribute in your implementation, with or without modification, any schemas, IDLs, or code samples that are included in the documentation. This permission also applies to any documents that are referenced in the Open Specifications documentation. No Trade Secrets. Microsoft does not claim any trade secret rights in this documentation. Patents. Microsoft has patents that might cover your implementations of the technologies described in the Open Specifications documentation. Neither this notice nor Microsoft's delivery of this documentation grants any licenses under those patents or any other Microsoft patents. However, a given Open Specifications document might be covered by the Microsoft Open Specifications Promise or the Microsoft Community Promise. If you would prefer a written license, or if the technologies described in this documentation are not covered by the Open Specifications Promise or Community Promise, as applicable, patent licenses are available by contacting [email protected].