Architecture Of The Linux Kernel

Architecture Of The Linux Kernel

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  Architecture of theLinux Kernel by Dominique Gerald M Cimafranca dominique.cimafranca@gmail.com This work is licensed under the Creative Commons Attribution-Share Alike 3.0 Philippines License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/ph/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
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  Fundamental Architecture User Applications User Space GNU C Library (glibc) System Call Interface Kernel Kernel Space Architecture Dependent Kernel Code Hardware Platform
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  User Space Components ● User applications ● glibc ● Provides the system call interface that connects to the kernel ● Provides the mechanism to transition between user- space application and kernel ● Each user space process occupies its own virtual address space (vs the kernel which runs on the single address space)
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  Kernel Space Components ● System Call Interface ● Provides the basic functions such as read() and write() ● Kernel ● Architecture-independent kernel code ● Common to all processor architectures supported by Linux ● Architecture-Dependent Code ● Processor- and platform-specific code ● Also known as Board Support Package
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  Kernel Subsystems System Call Interface Process Management Virtual File System Memory Management Network Stack Arch Device Drivers
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  System Call Interface ● Provides the means to perform function calls from user space into the kernel. ● This interface can be architecture dependent, even within the same processor family. ● Can be found in ● ./linux/kernel ● ./linux/arch
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  Process Management ● Focused on the execution of processes ● Each has an individual virtualization of the processor (thread code, data, stack, and registers) ● Kernel provides API through SCI to start, stop, and communicate with processes ● Processes are managed by a scheduler
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  Scheduler ● Kernel implements a scheduling algorithm ● Operates in constant time, regardless of threads ● O(1), meaning, same time to schedule one thread or many threads ● Can be found in ● ./linux/kernel ● ./linux/arch
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  Memory Management ● Memory is managed in pages ● Typically 4KB per page for most architectures ● Can be adjusted ● Support for hardware mechanisms for physical and virtual mappings, e.g. MMU on Pentium ● Keeps tracks of which pages are full, partially used, or empty ● Or if physical memory runs out, swap to disk ● Can be found in ./linux/mm
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  Virtual File System Virtual File System ext3 ... FAT32 /proc Buffer Cache Device Drivers Physical Devices
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  Virtual File System ● Presents a common API abstraction of functions such as open, close, read, and write ● Translates to abstractions specific to a file system ● Support for over 50 different file systems ● Can be found in ./linux/fs
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  Buffer Cache ● Caching layer that optimizes access to the physical devices by keeping data around for a short time ● Provides a common set of functions to the file system layer (independent of any particular file system)
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  Network Stack ● Follows a layered architecture modeled after the TCP/IP protocols ● TCP layer communicates with SCI via sockets ● Sockets provide a standard API to the networking subsystem ● Manage connections ● Move data between endpoints ● Can be found in ./linux/net
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  Device Drivers andArchitecture- Dependent Code ● Most of the Linux kernel source code consists of device drivers ● Can be found in ./linux/drivers ● While Linux kernel is mostly architecture ● Can be found in ./linux/arch
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  Questions?
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  References ● Anatomy of the Linux Kernel, M. Tim Jones, IBM Developerworks (http://www.ibm.com/developerworks/linux/library/l-linux-kernel/)
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  Architecture of theLinux Kernel by Dominique Gerald M Cimafranca dominique.cimafranca@gmail.com This work is licensed under the Creative Commons Attribution-Share Alike 3.0 Philippines License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/ph/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.