– August 7, 2013
Some time ago Konrad Rzeszutek Wilk (the Xen Linux maintainer) came up with a list of possible improvements to the Xen PV block protocol, which is used by Xen guests to reduce the overhead of emulated disks.
This document is quite long, and the list of possible improvements is also not small, so we decided to go implementing them step by step. One of the first items that seemed like a good candidate for performance improvement was what is called “indirect descriptors”. This idea is borrowed from the VirtIO protocol, and to put it clear consists on fitting more data in a request. I am going to expand how is this done later in the blog post, but first I would like to speak a little bit about the Xen PV disk protocol in order to understand it better.
Xen PV disk protocol
The Xen PV disk protocol is very simple, it only requires a shared memory page between the guest and the driver domain in order to queue requests and read responses. This shared memory page has a size of 4KB, and is mapped by both the guest and the driver domain. The structure used by the fronted and the backend to exchange data is also very simple, and is usually known as a ring, which is a circular queue and some counters pointing to the last produced requests and responses.
Posted in Xen Development, Xen Hypervisor.
– July 31, 2013
This is a joint blog post by Anil Madhavapeddy and Lars Kurth
As in previous years, the Xen Project had a presence at OSCON again. This year, we did not have our own booth: Citrix donated some space to a number of different open source projects in their Open @ Citrix booth and the Xen Project gladly took this offer. Like in the past, we had volunteers helping out at the booth. I wanted to thank Anil Madhavapeddy, George Dunlap, Ian Campbell, Richard Mortier and Russell Pavlicek for their work.
Posted in Community, Events.
– July 26, 2013
My name is Julien Grall. I joined the Citrix Open Source team few months ago to work on Xen on ARM with Ian Campbell and Stefano Stabellini. Since Citrix has joined the Linaro Enterprise Group (LEG), I’m also part of the virtualization team which takes care of Xen, KVM and QEMU within Linaro.
A couple of weeks ago, I have attended my first Linaro Connect Europe, held in Dublin from 8th to 12th of July. All the major players in the ARM world came together to discuss the future of the industry and build an healthy Open Source ecosystem for ARM.
Posted in Events, Xen Development.
– July 19, 2013
This has already been a banner year for the Xen Project. We have already seen the 10th anniversary of the project, the birth of Xen as a Linux Foundation Collaboration Project, and the release of version 4.3 of the Xen Project software. More than that, this is also the first year we are hosting three excellent community events:
- the Xen Project Hackathon in Dublin, Ireland in May
- the Xen Project User Summit in New Orleans. Louisiana, USA in September, and
- the Xen Project Developer Summit in Edinburgh, Scotland in October.
The Hackathon was a great success in May, and the Developer Summit promises to be a terrific close to the year in October, but the User Summit is on the immediate horizon.
What is the Xen Project User Summit?
In years past, the Xen Project has hosted a number of Xen Summits. These events were often a mixture of developer and user content, often with a majority of the sessions oriented toward developers. This year, we have split the former Xen Summit into two distinctly different events: one for developers, and one for users.
Posted in Announcements, Community, Events, Xen Summit.
– July 19, 2013
So, how many of you use Debian? I bet a lot. Well, here it is what the Debian Xen package maintainers told The Xen Project, when asked a few questions. We are talking about Bastian Blank and Guido Trotter. In fact, they share the burden, with Bastian doing “most of the work nowadays” (Guido’s words) and Guido “starting packaging Xen many years ago, while assisting with stable security updates lately” (ditto).
You’ll discover that they particularly like the Xen architecture, and this makes us really really proud. It also look like a shorter release cycle for Xen is in the wishlist. Well, Xen 4.3 cycle has already been way shorter than its predecessors, and the feeling is the future will be even better!
However, the most surprising thing is that coffee is quite unpopular with them too, as it was already the case for Maarten from Mageia… I am honestly starting to think whether this could be a ‘package maintainers’ thing’!
Anyway, sincere thanks to both Bastian and Guido for finding the time for this interview, and let’s get straight to their answers!
Posted in Community, Xen Case Study, Xen Development, Xen Hypervisor.
– July 9, 2013
Xenproject.org is pleased to announce the release of Xen 4.3.0. The release is available from the download page:
Xen 4.3 is the work of just over 9 months of development, with 1362 changesets containing changes to over 136128 lines of code, made by 90 individuals from 27 different organizations and 25 unaffiliated individual developers.
Xen 4.3 is also the first release made with using the roadmap to track what people were doing and aim for what to try to get into this release, as well as the first release to have consistent Xen test days. This, combined with the increased number of contributors, should make this one of the best Xen releases so far. Read on for more information.
Probably the biggest single feature of this release is the experimental support for ARM virtualization, both 32-bit and 64-bit variants. The 32-bit port of Xen boots on ARMv7 Fast Models, the Cortex A15 Versatile Express platform and the Arndale board (equipped with the Exynos5 SoC by Samsung). It can boot dom0, create other virtual machines and it supports all the basic virtual machine lifecycle operations. Hardware is not yet available for 64-bit ARM processors yet, but Xen is running well in 64-bit mode on AEMv8 Real-time System Models by ARM.
Posted in Announcements, Xen Development, Xen Hypervisor.
– July 4, 2013
Yes, apparently Schrödinger’s cat is alive, as the latest release of Fedora – Fedora 19, codename Schrödinger’s cat– as been released on July 2nd, and that even happened quite on time.
So, apparently, putting the cat ”in a box” and all the stuff was way too easy, and that’s why we are bringing the challenge to the next level: do you dare putting Schrödinger’s cat “in a virtual box”?
In other words, do you dare install Fedora 19 within a Xen virtual machine? And if yes, how about doing that using Fedora 19 itself as Dom0?
Posted in Uncategorized, Xen Case Study, Xen Hypervisor.
– June 28, 2013
As many of you might have (inevitably) noticed, Xen frontend / backend network drivers in Linux suffered from regression several months back after the XSA-39 fix (various reports here, here and here). Fortunately that’s now fixed (see the most important patch of that series) and the back-porting process to stable kernels is on-going. Now that we’ve put everything back into stable-ish state, it’s time to look into the future to prepare Xen network drivers for the next stage. I mainly work on Linux drivers, but some of the backend improvements ideas should benefit all frontends.
The goal is to improve network performance and scalability without giving up the advanced security feature Xen offers. Just to name a few items:
Split event channels: In the old network drivers there’s only one event channel between frontend and backend. That event channel is used by frontend to do TX notification and RX buffer allocation notification to backend. It is also used by backend to do TX completion and RX notification to frontend. So this is definitely not ideal as TX and RX interferes with each other. So with a little change to the protocol we can split TX and RX notifications into two event channels. This work is now in David Miller’s tree (patch for backend, frontend and document).
Posted in Xen Development.
– June 27, 2013
Xen 4.3.0 time is approaching and, to make sure we’re delivering the best possible release, we are having another Xen TestDay on Friday, June 28 2013. (RSVP and iCal here).
We will be testing Xen
4.3.0-RC6, that will be tagged on Thursday. It will ship two really important changes (as compared to RC5) about PCI passthrough and CPU hotplug. Help us making sure there are no issues left, both on those two specifically, and in general!
In fact, about the former, we’ve had to change the way Xen handles some aspects of PCI passthrough, to work around an issue with qemu-xen. We think we’ve got everything right, but please test your own configuration to make sure that it still works for you. We particularly need graphics cards with large amounts of video RAM tested. About the latter, CPU hotplug support was missing in qemu-xen, and it has now been implemented, so go ahead testing it (CPU hot-unplug is still not supported, though).
We will announce on the xen-devel (and other relevant) mailing lists when RC6 will become available. In the meanwhile, here they are the Xen 4.3 RC6 test instructions, while more information about Xen TestDays are available here.
Join us on Friday on the #xentest channel on freenode!
If nothing relevant comes up during the TestDay, the plan is to have the release next week, probably on July 2nd.
Posted in Uncategorized.
– June 25, 2013
Today, Citrix announced that XenServer would be fully open sourced and that it will be made available from XenServer.org. First, I wanted to remind everyone that XenServer always has been based on open source software: containing the Xen hypervisor, the Linux kernel, the CentOS Linux distribution and user tools. However many XenServer components were proprietary.
In 2009, Citrix released XAPI – the XenServer management toolstack – and the XCP ISOs – a variant of XenServer that predominantly contains open source components – under open source licenses on xen.org. This marked the beginning of XenServer’s transition towards open source. In 2011, XAPI packages were delivered into Debian and Ubuntu, enabling users to build a XenServer like system from individual packages. Earlier this year, XAPI moved with Xen.org under the auspices of the Xen Project – a Linux Foundation Collaborative Project. In other words, the XAPI project is now a sub-project of the Xen Project. The creation of XenServer.org as announced today concludes this journey towards open source.
Why is this good for our community?
One of the consequences of open sourcing XenServer components (aka XAPI) and XCP in stages was that it created confusion amongst developers and users. This was compounded because some software – such as the XCP build system – was not available as open source. The primary reason for this is that the source code, project and the packaging (XCP ISO and XAPI packages delivered into Linux distributions) were not cleanly defined.
Posted in Community.