Google Summer of Code 2020: Difference between revisions

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== Device Emulation ==
== Device Emulation ==
Internships/ProjectIdeas/NVMePerformance
{{:Internships/ProjectIdeas/NVMePerformance}}


== How to add a project idea ==
== How to add a project idea ==

Revision as of 17:11, 9 January 2020

Introduction

QEMU is applying to Google Summer of Code 2020. This page contains our ideas list and information for students and mentors. Google Summer of Code is an open source internship program for university students offering 12-week, full-time, paid remote work from May to August.

Applicants: You are welcome to think about project ideas and familiarize yourself with QEMU, but please don't invest too much time at this early stage. Google will announce participating organizations on February 20.

Application Process

1. Discuss the project idea with the mentor(s)

Read the project ideas list and choose one you are interested in. Read the links in the project idea description and start thinking about how you would approach this. Ask yourself:

  • Do I have the necessary technical skills to complete this project in 12 weeks?
  • Will I be able to work independently without the physical presence of my mentor?

If you answer no to these questions, choose another project idea and/or organization that fits your abilities better.

Once you have identified a suitable project idea, email the mentor(s) your questions about the idea and explain your understanding of the project idea to them to verify that you are on track.

2. Fill out the application form

The application 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.

3. IRC interview including a coding exercise

You may be invited to an IRC interview. The interview consists of a 30-minute 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 the programming language for your project idea (QEMU projects are typically in C but could also be in Python or Rust).

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.

Key Dates

From the timeline

  • March 16 - 31, 2020 - Student Applications
  • April 27, 2020 - Student Projects Announced

Find Us

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

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.

Device Emulation

NVMe Emulation Performance Optimization

Summary: QEMU's NVMe emulation uses the traditional trap-and-emulate method to emulate I/Os, thus the performance suffers due to frequent VM-exits. Version 1.3 of the NVMe specification defines a new feature to update doorbell registers using a Shadow Doorbell Buffer. This can be utilized to enhance performance of emulated controllers by reducing the number of Submission Queue Tail Doorbell writes.

Further more, it is possible to run emulation in a dedicated thread called an IOThread. Emulating NVMe in a separate thread allows the vcpu thread to continue execution and results in better performance.

Finally, it is possible for the emulation code to watch for changes to the queue memory instead of waiting for doorbell writes. This technique is called polling and reduces notification latency at the expense of an another thread consuming CPU to detect queue activity.

The goal of this project is to add implement these optimizations so QEMU's NVMe emulation performance becomes comparable to virtio-blk performance.

Tasks include:

  • Add Shadow Doorbell Buffer support to reduce doorbell writes
  • Add Submission Queue Tail Doorbell register ioeventfd support when the Shadow Doorbell Buffer is enabled (see existing patch linked below)
  • Add Submission Queue polling
  • Add IOThread support so emulation can run in a dedicated thread

Links:

Details:

  • Project size: 350 hours
  • Difficulty: intermediate to advanced
  • Required skills: C programming
  • Desirable skills: knowledge of the NVMe PCI specification, knowledge of device driver or emulator development
  • Mentor: Klaus Jensen <its@irrelevant.dk> (kjensen on IRC), Keith Busch <kbusch@kernel.org>
  • Suggested by: Huaicheng Li <huaicheng@cs.uchicago.edu>, Paolo Bonzini <pbonzini@redhat.com> ("bonzini" on IRC)

How to add a project idea

  1. Create a new wiki page under "Internships/ProjectIdeas/YourIdea" and follow #Project idea template.
  2. Add a link from this page like this: {{:Internships/ProjectIdeas/YourIdea}}

Example idea from a previous year: Internships/ProjectIdeas/I2CPassthrough

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

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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