X86 Assembly Language: AT&T and Intel
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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). -
Use of Seek When Writing Or Reading Binary Files
Title stata.com file — Read and write text and binary files Description Syntax Options Remarks and examples Stored results Reference Also see Description file is a programmer’s command and should not be confused with import delimited (see [D] import delimited), infile (see[ D] infile (free format) or[ D] infile (fixed format)), and infix (see[ D] infix (fixed format)), which are the usual ways that data are brought into Stata. file allows programmers to read and write both text and binary files, so file could be used to write a program to input data in some complicated situation, but that would be an arduous undertaking. Files are referred to by a file handle. When you open a file, you specify the file handle that you want to use; for example, in . file open myfile using example.txt, write myfile is the file handle for the file named example.txt. From that point on, you refer to the file by its handle. Thus . file write myfile "this is a test" _n would write the line “this is a test” (without the quotes) followed by a new line into the file, and . file close myfile would then close the file. You may have multiple files open at the same time, and you may access them in any order. 1 2 file — Read and write text and binary files Syntax Open file file open handle using filename , read j write j read write text j binary replace j append all Read file file read handle specs Write to file file write handle specs Change current location in file file seek handle query j tof j eof j # Set byte order of binary file file set handle byteorder hilo j lohi j 1 j 2 Close -
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. -
LECTURE NOTE 5: the MEMORY MANAGEMENT REAL MODE Allows the Microprocessor to Address Only the First 1Mbyte of Memory Even If Its Pentium II Microprocessor
LECTURE NOTE 5: THE MEMORY MANAGEMENT REAL MODE Allows the microprocessor to address only the first 1Mbyte of memory even if its Pentium II microprocessor. The first 1Mbyte of memory is called either the real mode or conventional memory system. The DOS operating system requires the microprocessor to operate in this mode. It allows application software. Segment and Offset Through the combination of these two, a memory location is accessed in the real mode. All real mode memory address must consist of a segment address plus an offset address. Segment Address Defines the beginning address of any 64k-byte memory segment. Offset Address Sometimes called displacement or relative. Selects any location within the 64k-byte memory segment. It is the distance above the start of the segment. Note: Each segment register is internally appended with a 0H on its right end. The segment address can begin only at a 16-byte boundary, which is called paragraph. Once the beginning address in known, an ending address is known, by adding FFFFH. The code segment register defines the start of the code segment and the instruction pointer to locate the next instruction within the code segment. This combination (CS:IP or CS:EIP) locates the next instruction executed by the microprocessor. Stack data are referenced through the stack segment at the memory location addressed by either the stack pointer (SP/ESP) or the base pointer (BP/EBP). These combinations are referred to as SS:SP (SS:ESP) or SS:BP (SS:EBP). Addressing Modes 1. Register Addressing Mode transfer a copy of a byte or word from the source register or memory location to the destination register or memory location. -
The Pentium Processor
Chapter 7 The Pentium Processor 7–1 The main purpose of registers is to provide a scratch pad so that the processor can keep data on a temporary basis. For example, the processor may keep the procedure return address, stack pointer, instruction pointer, and so on. Registers are also used to keep the data handy so that it can avoid costly memory accesses. Keeping frequently accessed data in registers is a common compiler optimization technique. 7–2 Pentium supports the following three address spaces: 1. Linear address space 2. Physical address space 3. I/O address space (from discussion in Section 1.7) 7–3 In segmented memory organization, memory is partitioned into segments, where each segment is a small part of the memory. In the real mode, each segment of memory is a linear contiguous sequence of up to 64 KB. In the protected mode, it can be up to 4 GB. Pentium supports segmentation largely to provide backward compatibility to 8086. Note that 8086 is a 16-bit processor with 20 address lines. This mismatch between the processor’s 16-bit registers and 20-bit addresses is solved by using the segmented memory architecture. This segmented architecture has been carried over to Pentium. However, in the protected mode, it is possible to consider the entire memory as a single segment; thus, segmentation is completely turned off. 7–4 In the real mode, a segment is limited to 64 KB due to the fact that 16 bits are used to indicate the offset value into a segment. This magic number 16 is due to the 16-bit registers used 8086 processor. -
I386-Engine™ Technical Manual
i386-Engine™ C/C++ Programmable, 32-bit Microprocessor Module Based on the Intel386EX Technical Manual 1950 5 th Street, Davis, CA 95616, USA Tel: 530-758-0180 Fax: 530-758-0181 Email: [email protected] http://www.tern.com Internet Email: [email protected] http://www.tern.com COPYRIGHT i386-Engine, VE232, A-Engine, A-Core, C-Engine, V25-Engine, MotionC, BirdBox, PowerDrive, SensorWatch, Pc-Co, LittleDrive, MemCard, ACTF, and NT-Kit are trademarks of TERN, Inc. Intel386EX and Intel386SX are trademarks of Intel Coporation. Borland C/C++ are trademarks of Borland International. Microsoft, MS-DOS, Windows, and Windows 95 are trademarks of Microsoft Corporation. IBM is a trademark of International Business Machines Corporation. Version 2.00 October 28, 2010 No part of this document may be copied or reproduced in any form or by any means without the prior written consent of TERN, Inc. © 1998-2010 1950 5 th Street, Davis, CA 95616, USA Tel: 530-758-0180 Fax: 530-758-0181 Email: [email protected] http://www.tern.com Important Notice TERN is developing complex, high technology integration systems. These systems are integrated with software and hardware that are not 100% defect free. TERN products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices, or systems, or in other critical applications. TERN and the Buyer agree that TERN will not be liable for incidental or consequential damages arising from the use of TERN products. It is the Buyer's responsibility to protect life and property against incidental failure. TERN reserves the right to make changes and improvements to its products without providing notice. -
Xv6 Booting: Transitioning from 16 to 32 Bit Mode
238P Operating Systems, Fall 2018 xv6 Boot Recap: Transitioning from 16 bit mode to 32 bit mode 3 November 2018 Aftab Hussain University of California, Irvine BIOS xv6 Boot loader what it does Sets up the hardware. Transfers control to the Boot Loader. BIOS xv6 Boot loader what it does Sets up the hardware. Transfers control to the Boot Loader. how it transfers control to the Boot Loader Boot loader is loaded from the 1st 512-byte sector of the boot disk. This 512-byte sector is known as the boot sector. Boot loader is loaded at 0x7c00. Sets processor’s ip register to 0x7c00. BIOS xv6 Boot loader 2 source source files bootasm.S - 16 and 32 bit assembly code. bootmain.c - C code. BIOS xv6 Boot loader 2 source source files bootasm.S - 16 and 32 bit assembly code. bootmain.c - C code. executing bootasm.S 1. Disable interrupts using cli instruction. (Code). > Done in case BIOS has initialized any of its interrupt handlers while setting up the hardware. Also, BIOS is not running anymore, so better to disable them. > Clear segment registers. Use xor for %ax, and copy it to the rest (Code). 2. Switch from real mode to protected mode. (References: a, b). > Note the difference between processor modes and kernel privilege modes > We do the above switch to increase the size of the memory we can address. BIOS xv6 Boot loader 2 source source file executing bootasm.S m. Let’s 2. Switch from real mode to protected mode. expand on this a little bit Addressing in Real Mode In real mode, the processor sends 20-bit addresses to the memory. -
X86 Memory Protection and Translation
2/5/20 COMP 790: OS Implementation COMP 790: OS Implementation Logical Diagram Binary Memory x86 Memory Protection and Threads Formats Allocators Translation User System Calls Kernel Don Porter RCU File System Networking Sync Memory Device CPU Today’s Management Drivers Scheduler Lecture Hardware Interrupts Disk Net Consistency 1 Today’s Lecture: Focus on Hardware ABI 2 1 2 COMP 790: OS Implementation COMP 790: OS Implementation Lecture Goal Undergrad Review • Understand the hardware tools available on a • What is: modern x86 processor for manipulating and – Virtual memory? protecting memory – Segmentation? • Lab 2: You will program this hardware – Paging? • Apologies: Material can be a bit dry, but important – Plus, slides will be good reference • But, cool tech tricks: – How does thread-local storage (TLS) work? – An actual (and tough) Microsoft interview question 3 4 3 4 COMP 790: OS Implementation COMP 790: OS Implementation Memory Mapping Two System Goals 1) Provide an abstraction of contiguous, isolated virtual Process 1 Process 2 memory to a program Virtual Memory Virtual Memory 2) Prevent illegal operations // Program expects (*x) – Prevent access to other application or OS memory 0x1000 Only one physical 0x1000 address 0x1000!! // to always be at – Detect failures early (e.g., segfault on address 0) // address 0x1000 – More recently, prevent exploits that try to execute int *x = 0x1000; program data 0x1000 Physical Memory 5 6 5 6 1 2/5/20 COMP 790: OS Implementation COMP 790: OS Implementation Outline x86 Processor Modes • x86