Participating in the kernel development process

Transcription

1 Participating in the kernel development process (With a minimum of pain) Jonathan Corbet LWN.net corbet@lwn.net

2 What we'll talk about An introduction to the kernel community Why be a part of it? The Kernel Report Licensing, copyright, and lawyers Some overall principles The mechanics of kernel contribution Hints 1: Process Hints 2: Code Tools Conclusion

3 Ask anytime! Questions?

4 About your speaker Kernel hacker since 1980 Linux since 1993 Co-founded LWN in 1998 Co-author of Linux Device Drivers Maintainer: cafe-ccic, ov7670, and via-camera drivers Author: Documentation/development-process Kernel Summit program committee member Linux Foundation Technical Advisory Board member Worldwide speaker on Linux kernel topics

5 What is the kernel?

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7 The kernel... Makes the hardware work Manages processes Enforces security Communicates with other systems Implements filesystems...

8 Kernel programming is unique

9 Kernel programming is unique Low-level programming environment (No C library)

10 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results

11 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results Performance is critical

12 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results Performance is critical High degree of concurrency

13 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results Performance is critical High degree of concurrency Wide range of target platforms Supercomputers Desktops Telephones

14 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results Performance is critical High degree of concurrency Wide range of target platforms Supercomputers Desktops Telephones Large, complex code base (>8M lines of code)

15 Kernel programming is unique Low-level programming environment (No C library) Failures are catastrophic Death of process at the minimum System failure or security breach often results Performance is critical High degree of concurrency Wide range of target platforms Supercomputers Desktops Telephones Large, complex code base (>8M lines of code) Huge, active development community

16 Developers contributing to each kernel release Release Developers , , , , , ,136

17 through rc7 (Feb 25, 2010 to March 6, 2011) Four major kernel releases (+ one in progress) 49,100 distinct changes merged (131 changes/day, every day) 1.3 million lines added (3,475 lines per day) 2,826 developers involved

18 About those 2,826 developers...they work for 326 companies that we have been able to identify.

19 Who those developers work for nobody 17.6% Red Hat 11.7% unknown 7.7% Intel 6.7% Novell 4.8% IBM 3.7% Nokia 2.3% Consultants 2.2% Texas Inst. 2.2% Oracle 1.7% AMD 1.6% Samsung 1.5% academics 1.4% Fujitsu 1.4% Renesas Tech. 1.4% Pengutronix 1.3% Google 1.2% Broadcom 1.1% Atheros 1.1% Analog Devices 1.1% Wolfson Micro 1.0% New Dream Net 1.0%

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21 In other words Over 75% of kernel patches come from people paid for their work

22 In other words Over 75% of kernel patches come from people paid for their work Linux is not the product of kids working in their parents' basements

23 In other words Over 75% of kernel patches come from people paid for their work Linux is not the product of kids working in their parents' basements These companies have solid reasons for contributing to the kernel

24 In other words Over 75% of kernel patches come from people paid for their work Linux is not the product of kids working in their parents' basements These companies have solid reasons for contributing to the kernel They have found ways to contribute successfully.

25 One other note Very few kernel developers do it full time

26 If development projects are communities......the kernel is a large city

27 Getting around in the city is not hard...once you know how it works.

28 Otherwise... So, I've had enough. I'm out of here forever. I want to leave before I get so disgruntled that I end up using Windows. I may play occasionally with userspace code but for me the kernel is a black hole that I don't want to enter the event horizon of again -- Con Kolivas 28

29 So why bother? 29

30 Why? The kernel is the core of a Linux system 30

31 Why? It's how you get the kernel to meet your needs Well, this is open source... you don't get to request new features, you get to implement them -- James Bottomley 31

32 Why? Out-of-tree code is lower quality code 32

33 Why? In-tree code can be improved by others 33

34 Why? You'll make your users and customers happy

35 Why? Out-of-tree code is expensive 35

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38 Google's code costs 300,000 lines of code 1200 patches 30 full-time kernel engineers

39 Why so expensive? The kernel is a moving target Duplicated work Often incompatible with in-tree solutions Nobody will help you maintain out-of-tree code No design guidance from the community...

40 Fun

41 Why? That is how our community works 41

42 Questions?