Architecture Of The Linux Kernel

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Overview of the Linux Kernel, based on "Anatomy of the Linux Kernel" by M. Tim Jones, (IBM Developerworks) http://www.ibm.com/developerworks/linux/library/l-linux-kernel/

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Architecture Of The Linux Kernel

  1. 1. Architecture of the Linux 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.
  2. 2. Fundamental Architecture User Applications User Space GNU C Library (glibc) System Call Interface Kernel Kernel Space Architecture Dependent Kernel Code Hardware Platform
  3. 3. 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)
  4. 4. 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
  5. 5. Kernel Subsystems System Call Interface Process Management Virtual File System Memory Management Network Stack Arch Device Drivers
  6. 6. 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
  7. 7. 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
  8. 8. 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
  9. 9. 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
  10. 10. Virtual File System Virtual File System ext3 ... FAT32 /proc Buffer Cache Device Drivers Physical Devices
  11. 11. 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
  12. 12. 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)
  13. 13. 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
  14. 14. Device Drivers and Architecture- 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
  15. 15. Questions?
  16. 16. References ● Anatomy of the Linux Kernel, M. Tim Jones, IBM Developerworks (http://www.ibm.com/developerworks/linux/library/l-linux-kernel/)
  17. 17. Architecture of the Linux 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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