Google Summer of Code 2017

From QEMU

Introduction

QEMU is applying for Google Summer of Code 2017. This page contains our ideas list and information for students and mentors. Google Summer of Code is a program that pays students for 12-week full-time remote work on open source projects from May to August!

Students: Google has not published the list of accepted organizations yet. You are welcome to contribute to QEMU and contact mentors for project ideas you are interested in. Please keep in mind that QEMU may not be accepted into GSoC to avoid disappointment.

Application Process

After contacting the mentor to discuss the project idea you should fill out the application form at [1]. The form asks for a problem description and outline of how you intend to implement a solution. You will need to do some background research (looking at source code, browsing relevant specifications, etc) in order to form an idea of how to tackle the project. The form asks for an initial 12-week project schedule which you should create by breaking down the project into tasks and estimating how long they will take. The schedule can be adjusted during the summer so don't worry about getting everything right ahead of time.

Candidates may be invited to an IRC interview with the mentor. The interview consists of a 30 minute C coding exercise, followed by technical discussion and a chance to ask questions you have about the project idea, QEMU, and GSoC. The coding exercise is designed to show fluency in C programming.

Here is a C coding exercise we have used in previous years when interviewing students: 2014 coding exercise

Try it and see if you are comfortable enough writing C. We cannot answer questions about the previous coding exercise but hopefully it should be self-explanatory.

If you find the exercise challenging, think about applying to other organizations where you have a stronger technical background and will be more competitive compared with other candidates.

Find Us

  • IRC (GSoC specific): #qemu-gsoc on irc.oftc.net
  • IRC (development):
    • QEMU: #qemu on irc.oftc.net
    • libvirt: #virt on irc.oftc.net
    • KVM: #kvm on chat.freenode.net

Please contact the mentor for the project idea you are interested in. IRC is usually the quickest way to get an answer.

For general questions about QEMU in GSoC, please contact the following people:

Project Ideas

This is the listing of suggested project ideas. Students are free to suggest their own projects, see #How to propose a custom project idea below.

Disk Backup Tool

Summary: Write a tool that performs both full and incremental disk backups

QEMU has added command primitives that can be combined to perform both full and incremental disk backups while the virtual machine is running. A full backup copies the entire contents of the disk. An incremental backup copies only regions that have been modified. Orchestrating a multi-disk backup to local or remote storage is non-trivial and there is no example code showing how to do it from start to finish.

It would be helpful to have a "reference implementation" that performs backups using QEMU's QMP commands. Backup software and management stack developers wishing to add QEMU backup support could look at this tool's code as an example. Users who run QEMU directly could us this tool as their backup software.

You need to be able to read C since that's what most of QEMU is written in. This project will expose you to backup and data recovery, as well as developing command-line tools in Python.

See the links to familiarize yourself with disk image files, backups, and snapshots.

Links:

Details:

  • Skill level: intermediate
  • Language: Python
  • Mentors: John Snow <jsnow@redhat.com> (jsnow on IRC), Stefan Hajnoczi <stefanha@redhat.com> (stefanha on IRC)

Moving I/O throttling and write notifiers into block filter drivers

Summary: Refactor the block layer so that I/O throttling and write notifiers are implemented as block filter drivers instead of being hardcoded into the core code

QEMU's block layer handles I/O to disk image files and now supports flexible configuration through a "BlockDriverState graph". Block drivers can be inserted or removed from the graph to modify how I/O requests are processed.

Block drivers implement read and write functions (among other things). Typically they access a file or network storage but some block drivers perform other jobs like data encryption. These block drivers are called "filter" drivers because they process I/O requests but ultimately forward requests to the file format and protocol drivers in the leaf nodes of the graph.

I/O throttling (rate-limiting the guest's disk I/O) and write notifiers (used to implement backup) are currently hardcoded into the block layer's core code. The goal of this project is to extract this functionality into filter drivers that are inserted into the graph only when a feature is needed. This makes the block layer more modular and reuses the block driver abstraction that is already present.

This project will expose you to QEMU's block layer. It requires refactoring existing code for which there is already some test coverage to aid you.

Links:

Details:

  • Skill level: intermediate
  • Language: C
  • Mentor: Kevin Wolf <kwolf@redhat.com> (kwolf on IRC), Stefan Hajnoczi <stefanha@redhat.com> (stefanha on IRC), Alberto Garcia (berto on IRC)

Project idea template

=== TITLE ===
 
 '''Summary:''' Short description of the project
 
 Detailed description of the project.
 
 '''Links:'''
 * Wiki links to relevant material
 * External links to mailing lists or web sites
 
 '''Details:'''
 * Skill level: beginner or intermediate or advanced
 * Language: C
 * Mentor: Email address and IRC nick
 * Suggested by: Person who suggested the idea

How to propose a custom project idea

Applicants are welcome to propose their own project ideas. The process is as follows:

  1. Email your project idea to qemu-devel@nongnu.org. CC Stefan Hajnoczi <stefanha@gmail.com> and regular QEMU contributors who you think might be interested in mentoring.
  2. If a mentor is willing to take on the project idea, work with them to fill out the "Project idea template" above and email Stefan Hajnoczi <stefanha@gmail.com>.
  3. Stefan will add the project idea to the wiki.

Note that other candidates can apply for newly added project ideas. This ensures that custom project ideas are fair and open.

How to get familiar with our software

See what people are developing and talking about on the mailing lists:

Grab the source code or browse it:

Build QEMU and run it: QEMU on Linux Hosts

Important links

Information for mentors

Mentors are responsible for keeping in touch with their student and assessing the student's progress. GSoC has a mid-term evaluation and a final evaluation where both the mentor and student assess each other.

The mentor typically gives advice, reviews the student's code, and has regular communication with the student to ensure progress is being made.

Being a mentor is a significant time commitment, plan for 5 hours per week. Make sure you can make this commitment because backing out during the summer will affect the student's experience.

The mentor chooses their student by reviewing student application forms and conducting IRC interviews with candidates. Depending on the number of candidates, this can be time-consuming in itself. Choosing the right student is critical so that both the mentor and the student can have a successful experience.

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