zz:news.com:Xen getting multiprocessor support

bbbush

CNET News.com    http://www.news.com/
Xen getting multiprocessor support

By Stephen Shankland
http://news.com.com/Xen+getting+ ... 7344_3-5741373.html

Story last modified Mon Jun 13 04:00:00 PDT 2005



Xen, software that lets multiple operating systems run on the same computer, will become significantly more powerful with an upcoming version that introduces multiprocessor support.

Xen is a "hypervisor"--a thin layer of software that governs how different operating systems get access to computer resources such as processors and memory. But the current version is hobbled by the fact that each operating system can use only one processor.

Version 3, which programmers hope to begin testing this month, will lift that limit, said Ian Pratt, a founder and lead programmer of the open-source project and the company XenSource that's trying to commercialize it. "We hope to get 3.0.0 out in August--sooner if we're ready," Pratt said, though he cautioned, "I'm a firm believer in having releases driven by product quality rather than dates."

News.context

What's new:
A new level of maturity is planned for Xen, open-source software that lets multiple operating systems run on the same computer. With version 3, an OS running on top of Xen will be able to tap into the power of more than one processor.

Bottom line:
Multiprocessor support should help Xen become useful for higher-end servers and measure up better against rival technology such as EMC's VMware.

More stories on Xen
The multiprocessor support is important, said Illuminata analyst Gordon Haff. "Some applications obviously need more than one processor's worth of performance," he said, and Xen also stands to benefit from not being pigeonholed as software with only limited abilities.

Running multiple operating systems on a single machine--an ability that Unix servers and mainframes have had for years--is useful for several reasons. It makes it easier for one server to share multiple tasks and therefore replace several independent machines. And personal computers can be divided into noninterfering domains for business use, personal use or systems management. Mainstream adoption of multi-OS practices likely will be hastened by features in Intel processors this year and Advanced Micro Devices chips in 2006 that make the task significantly easier.

Xen has gained active help from Intel, IBM, AMD, Hewlett-Packard, Sun Microsystems, Red Hat and Novell. In prevailing industry argot, its job is to virtualize computer resources, letting operating systems run in separate "virtual machines," often called partitions, rather than directly on the hardware itself.

But Xen also has rivals to fend off. EMC subsidiary VMware has a head start of years, already supports virtual machines that use up to two physical processors, and will receive four-processor support by the end of 2005. And Microsoft is working on its own hypervisor, a product expected to ship in 2007.

Another potentially formidable competitor could have been IBM's rHype, or Research Hypervisor, given that Big Blue has decades of experience with the technology. But in a mailing list posting, an IBM programmer said the project--or at least the version for Intel chips--"was mostly for demonstration purposes" and steered people toward Xen.

Xen uses an approach called paravirtualization that stops a step short of the full-on virtualization used by market leader VMware. That approach boosts performance, Pratt and analysts agree, but today requires that operating systems be modified to take advantage of it. The top Linux sellers, Red Hat and Novell, have released test versions of their open-source operating system products with tentative support.

Paravirtualization means that Xen doesn't face some VMware limits for multiprocessor servers. "I've seen excellent results on eight-way systems--that's the biggest we have access to--but I know people are using Xen on some 32-way systems," Pratt said.

Other Xen 3 features
Multiprocessor support isn't the only change coming. Also on tap is support for Intel's Virtualization Technology (VT), which is expected to ease Xen's operating system compatibility, and support for the 64-bit extensions that expand memory capacity for newer x86 processors such as Intel's Xeon and Advanced Micro Devices' Opteron.

Further improvements are planned for later updates to version 3, Pratt said. One is a "shared buffer cache," which would let separate partitions share a processor's high-speed cache memory for faster data access. Another is faster networking links among different virtual machines using an approach that will work even if a virtual machine is moved from one physical computer to another.

AMD's answer to Intel's VT is a technology code-named Pacifica. Xen support for Pacifica is a "work in progress," Pratt said.

It's likely a single version of Xen will be able to support both VT and Pacifica, Pratt said.

Details on how that is likely to happen emerged in June, when AMD programmer Elsie Wahlig proposed on Xen's mailing list a common interface to the two technologies. Wahlig worked with Pratt, another lead Xen programmer named Keir Fraser, and IBM to develop the proposal.

Intel's Jun Nakajima said Intel would help modify Xen to accommodate the change. "We are evaluating this proposal and will work on enhancing the VT-x code to provide the right level of abstraction to support other VT-x like technologies," Nakajima said. VT-x refers to the version of VT that runs on Intel's Xeon processors, as opposed to VT-i for its Itanium chips.

Xen still has a ways to go, however, Haff said. "Xen remains relatively immature compared to VMware in particular," he said. "We'll be able to say it's truly mature when it gets rolled into enterprise Linux distributions and has all the ancillary command and control tools."

High-stakes start-ups
IBM's renewed Power supply
Developers get taste of Intel-based Macs
Xen getting multiprocessor support
Previous Next
Another requirement for virtual machine software will be to get certification from software companies, said Gabriel Consulting Group analyst Daniel Olds. "That's a killer in the corporate environment and will keep VMware and Xen on the outside looking in" until it's addressed, he said.

The BitKeeper snafu
Xen developers are going through some of the same growing pains as the Linux operating system with which Xen is closely allied. In April, Linux programmers abruptly shifted to a new mechanism to control the project's underlying source code, and now Xen is facing the same plight.

Linux and Xen programmers had managed their source code with a proprietary tool called BitKeeper from a company called BitMover. BitMover had permitted open-source programmers to use the tool, but the company canceled the offer this year.

"The BitKeeper issue has come at a very bad time for us, as we really don't want to change (source code managers) until 3.0 ships," Pratt said.

And there aren't any simple fixes, he added. "We're strongly considering buying some BitKeeper licenses for the key developers to tide us over. We tried a bunch of different tools, and none of them come close to BitKeeper," Pratt said.

BitMover released a tool last week to ease the transition, though. The tool lets a BitKeeper source code repository be converted to a widely used alternative, Concurrent Version System, or CVS.


Copyright ©1995-2005 CNET Networks, Inc. All rights reserved.

Xen getting multiprocessor support

bbbush

Red Hat virtually supports Xen with Fedora Core 4
15th June 2005
By CBR Staff Writer
Red Hat's Fedora Linux project has released Fedora Core 4, introducing support for the Xen open source virtualization project for the first time with the latest version of its community-developed operating system.
Advertisement

The community-led project provides an early view of technologies likely to be included in future releases of Red Hat's Enterprise Linux distribution, and is the first concrete evidence that the Raleigh, North Carolina-based company will introduce support for Xen into RHEL.

Created and distributed by XenSource, Xen is an open source virtualization hypervisor that has already received the backing of IBM, Hewlett-Packard, Intel, and Advanced Micro Devices, among others.

Red Hat began talking positively about Xen in October 2004 but until now no concrete plans have been announced. Red Hat's Linux rival, Novell, introduced support for Xen in its SuSE Linux Professional 9.3 consumer product released in April.

Alongside Xen, Fedora Core 4 also provides an early look at OpenOffice.org 2.0, the new version of the open source office productivity applications suite, which is not yet generally available, as well as Evince, a new document viewer for PDF and Postscript files from the Gnome project.

Fedora Core 4 also includes version 2.10 of the Gnome interface, version 3.4 of the KDE interface, version 3.1 of the Eclipse development environment, as well as Red Hat's Global File System integrated clustering technology.

While Red Hat Enterprise Linux has long been available for Power processor-based servers, as well as including 32-bit X86, AMD64 and Intel EM64T, Intel Itanium 2, and IBM S/390 processor systems, Fedora Core 4 is the first Fedora release to also be available on PowerPC. According to the release notes, Fedora Core 4 should boot on Apple Computer's Macintosh PowerPC-based machines.

Earlier this month, Red Hat announced plans to hand over control of its Fedora community-led Linux development project to the new Fedora Foundation, moving Fedora project development work and copyright of contributed code outside of its core business.

An open letter to the current Fedora community from Karen Bennet, Red Hat vice president of applications and tools, indicates that not too much is expected to change. "There are no current plans to change the Fedora Core distribution project, processes, and management," she wrote. "As many have asked, Red Hat will also maintain ultimate overall control of the project to ensure that we continue to have timely, high quality releases."

However, according to Bennet, the Foundation could encourage new projects to develop under the Fedora umbrella without specific Red Hat involvement. "Fedora can only expand by enabling individuals and groups to contribute rather than consume. The Foundation exists to do this, not just for Red Hat originated Fedora projects but for those that come from the community," she said.

©2005 Business Review Ltd
Privacy | Bookmark Us | Advertising
©2005 Business Review Ltd
Return to CBR Online

http://www.cbronline.com/article ... D-869B-A71E5A4750E8

bbbush

A look at Xen

June 22, 2005
This article was contributed by Joe 'Zonker' Brockmeier.
The Xen virtual machine monitor is starting to pop up all over the place, or at least in several Linux distributions. Fedora Core 4 comes with Xen packaged as part of the release. SUSE Professional 9.3 includes Xen, there's the Xenophilia Linux distribution that is based around Xen, and Xen is in Debian unstable as well. XenSource, a company founded by Xen project developers, has also been in the news, and is getting funding from Kleiner Perkins Caufield & Byers and Sevin Rosen Funds as well as technology contributions from Intel.

This seems like a good time to take a look at Xen, see what it's capable of, and where it's going. We decided to test out Xen in Fedora Core 4, and the latest release from the Xen project in the form of a live CD to see how mature Xen is. According to the Xen Quickstart guide, Xen in FC4 is based on the Xen unstable tree, so some features will be a bit rough. Users who want to test Xen without installing FC4 can download demo CDs based on Debian from the Xen website. We also spoke with XenSource's Simon Crosby, a founder of XenSource and former professor at the University of Cambridge where Xen got its start.

Xen is a "hypervisor," or virtual machine monitor, which can execute several virtual machines on a single piece of hardware. Xen isn't unique in being able to run virtual hosts -- Linux users can run virtual machines using User-Mode Linux (UML), bochs, VMware products, SWsoft's Virtuozzo and a number of other virtualization technologies.

Xen operates a bit differently, however, than UML or VMware Workstation. Xen requires that a OS be ported to run on Xen's hypervisor, rather than attempting to emulate an x86 virtual machine completely as VMware Workstation does. The Xen approach is supposed to offer superior performance -- a performance comparision between VMware Workstation, Xen, native Linux and UML is available on the Xen website -- but it means that unmodified operating systems will not run on top of Xen. Users who want to run a virtual instance of Microsoft Windows, for example, will have to look elsewhere, at least for now. Crosby said that work is being done that will allow unmodified guest OSes to run on top of Xen, but that won't be complete until some time after 3.0 is released.

Also, Xen runs only on x86 systems with 686 processors or better, though ports to x86_64 and other processors are in progress. Crosby said that IBM is working on Power5 support, HP is working on Xen on IA64 and that he believes Sun is working on a Sparc port as well. The current Xen release will run on SMP systems, but does not include SMP support for guests. However, Crosby said that work is being done in this area, and the 3.0 roadmap calls for SMP support within guest hosts as well.

In addition to allowing a system to run multiple instances of Linux, Xen also works with NetBSD and FreeBSD, so users aren't restricted to using a Linux host for running Xen. Using the Xen live CD, we ran instances of Debian with the 2.4 and 2.6 series kernels alongside instances of FreeBSD and NetBSD.

We installed the Fedora Core 4 with the default "Workstation" set of packages. Xen's packages are not installed by default so we used Yum to grab the Xen host kernel, the Xen guest kernel and support packages. Xen in FC4 still requires a great deal of manual setup. There's no point-and-click GUI interface included to allow easy creation of Xen virtual hosts, and some users might find the steps to setting up Xen to be somewhat daunting. We followed along with the Fedora+Xen Quickstart guide to install Xen and create virtual hosts, and the Xen users' manual to get started with the basic Xen utilities.

After installing the Xen0 kernel, we disabled SELinux support and restarted the host to boot into the Xen0 kernel. SELinux needs to be disabled in order to create the guest filesystems. After rebooting, we created a 2GB file to use for the filesystem and then installed the Fedora Core 4 base system using Yum. It is also possible to export block devices directly to guest domains, so users could choose to use entire partitions for Xen guest filesystems.

After creating the filesystem, and creating a configuration file for the guest system under /etc/xen, we started up the guest host. We gave the guest 128 MB of RAM on a system with 1 GB total. We then tested the system a bit by creating a network interface, installing Apache with Yum and so on. The guest and host performance seemed fine, even when we started up a second guest with the same configuration on the same machine.

Xen also includes a web-based control interface. This interface didn't work in FC4, but worked just fine with the Xen live CD. After firing up "xensv" we were able to connect to the localhost on port 8080 and perform most of the functions available via the command line using the web-based interface.

The control interface for Xen is adequate, but certainly won't be winning any awards for ease of use. Crosby acknowledged that "you have to be something of a guru to use it," but noted that Xen's is very polished in the area of stability. Indeed, we didn't run into any stability issues with Xen while testing, and it looks like it's already suitable for utility computing. Crosby noted that XenSource is running its website and other services within Xen hosts.

Another interesting feature in Xen is the ability to move Xen instances from one physical machine to another. Crosby said that it's possible to move a Xen virtual machine "so that the guest is only non-responsive to the outside world for tens of miliseconds."

Xen 3.0 is scheduled for sometime in the July time frame according to the Xen roadmap. Crosby said that 3.0 will fork "in a few weeks time," and that the Xen team was waiting on a few features from the community before forking. When 3.0 forks in July, Crosby said that the Xen team would be working with the community, partners and distributions to hammer out the bugs.

We also talked to Crosby about the direction of XenSource, and whether its future offerings would be released as open source. Crosby said that the company planned to ship some proprietary tools for use with Xen, though Xen would continue to be open source. He also said that XenSource is interested in a world where the hypervisor is "ubiquitous" and provides an ecosystem with "a whole load of opportunities for vendors to compete in, creating a big pie... and we aim to have a fair slice of that pie."

While Xen is still a little rough around the edges, it's well worth a look for users who want a free software solution for virtualization. Xen's performance seems very good, and it looks like a good solution for Linux testing and perhaps web hosting and so forth. Given the interest from investors, Intel, SUSE, Red Hat and others, it seems likely that Xen will continue to improve at a rapid pace.
Post a comment

  A look at Xen
(Posted Jun 23, 2005 2:07 UTC (Thu) by subscriber yodermk) (Post reply)

>>> Crosby said that it's possible to move a Xen virtual machine "so that the guest is only non-responsive to the outside world for tens of miliseconds."

That sounds great, but I'm not sure I believe it. Wouldn't it take at least a few seconds to transfer an image to another box over 100 megabit ethernet?

Also, I read very briefly in a comment somewhere else that next-gen chips from Intel and AMD would allow for full virtualization without a modified guest, just as mainframes have done for decades. Does anyone know more about this and when they will come out? Will Xen support them right off the bat?

  A look at Xen
(Posted Jun 23, 2005 3:26 UTC (Thu) by subscriber dcreemer) (Post reply)

Xen guest VM migration between hosts completes very quickly. The actual transfer takes longer, but the VM stays running on the source machine as long as possible. It only (usually) takes less than a second to stop the VM on the source host, transfer any remaining differences, then bring up the VM on the target machine.

  A look at Xen
(Posted Jun 23, 2005 18:04 UTC (Thu) by subscriber patha) (Post reply)

> It only (usually) takes less than a second to stop the VM on the source host, transfer any remaining differences, [...]

Does this also holds for a machine with 64GB RAM running GUPS (http://www.dgate.org/~brg/files/dis/gups/) all over the memory? ;)

Seriously, were can I read about how the step "transfer any remaining differences" is implemented?

  A look at Xen
(Posted Jun 30, 2005 14:32 UTC (Thu) by guest MarkWilliamson) (Post reply)

For details of live migration see:
http://www.cl.cam.ac.uk/netos/papers/2005-migration-nsdi-...

Other papers under:
http://www.cl.cam.ac.uk/Research/SRG/netos/xen/architectu...

If you run software that dirties large amounts of memory then the precopy
approach doesn't work very well: in this case, the live migration code
will figure it out and cuts its losses by doing "stop and copy" -
incurring a longer stoppage but more efficient use of network bandwidth.

For real world server workloads it works well: Running Quake 3 servers
incurred a downtime of about 60ms (I think), whilst an Apache webserver
running SpecWeb incurred a downtime of 300ms and didn't drop any clients.

  A look at Xen
(Posted Jun 24, 2005 22:24 UTC (Fri) by subscriber erich) (Post reply)

Hi,
according to talk recently at BaLUG, they copy and note which pages have become "dirty" in the meantime, after a few cycles they then stop the vm and migrate the rest over, start it on the new one.
According to them, they've done that with a Quake3 server without the users noticing much. That sounds really impressive.
Apparently "downtimes" of ~200ms is typical when you have a 100Mbit link between the two hosting machines.

  A look at Xen
(Posted Jun 26, 2005 8:40 UTC (Sun) by subscriber csamuel) (Post reply)

Both Intel and AMD have made public declarations of support for Xen with respect to their virtualisation technology.

It's this which will make it possible to run unmodified OS's under Xen in the future (fingers crossed)..

Chris

  A look at Xen
(Posted Jun 23, 2005 15:32 UTC (Thu) by subscriber maceto) (Post reply)

wow Redhat needs yast, that`s way! easier on suse to setup, it`s like vmware vs dos...

  A look at Xen
(Posted Jun 24, 2005 17:21 UTC (Fri) by subscriber tsinclai) (Post reply)

I've been following this project for quite some time and am looking forward to trying it out.

As a technical instructor, this would seem to make setting up a virtual network in a classroom
much easier. Our Windows classes use Virtual PC for that purpose right now, but I prefer a
Free (as well as free) solution.

Am I right in thinking that Xen takes a different tack than VMWare?

  A look at Xen
(Posted Jun 24, 2005 23:34 UTC (Fri) by subscriber erich) (Post reply)

Do you know the basics of OS programming? About the ring model?
They are mentioned in http://en.wikipedia.org/wiki/X86

Xen runs in ring-0, requiring the OS to run in the lower rings.
Usually linux itself is in ring 0; userspace apps run in ring 2 or 3.
Basically, inner rings have more privileges, and are protected from outer rings.
Xen manages the memory on a high level, and linux instead of just handling memory itself, requests memory from xen via special calls. Basically thats the same way, the linux kernel is protected from userspace applications.

If Linux would try to do it directly, it would cause a segmentation fault; but having this protection, it cannot trash xen or the other vms.

VMWare probably detects these calls in the binary and replaces that code. VMware is MUCH closer to emulating a separate PC; Xen just takes away some privileges from the OS in order to separate them, and requires the OS to "politely ask" for the resources. Thats why you need a different kernel.
But since everything accessing the hardware is handled by the linux kernel, all changes needed for Xen are within the kernel.

  linux-vserver.org?
(Posted Jun 30, 2005 8:34 UTC (Thu) by guest gvy) (Post reply)

For "utility computing" everyone already uses VServer ;-) (which "only" allows for contexts within the same Linux kernel but that suffices for a wide range of applications, hosting/testing/resource provisioning being the most evident)

It's in a different weight but still the same category of virtualization software, and I wonder why mention UML (which is basically dead to me) and Virtuozzo (which is proprietary) and forget of VServer.

PS: shameless plug: yes, ALT Linux has the support out-of-box with 2.4 release. :-)

  no nptl though.
(Posted Jun 30, 2005 19:15 UTC (Thu) by guest zojas) (Post reply)

the lack of nptl support was a killer for me. I wanted to run a virtual redhat advanced server 3 using gentoo as a host system. but the whole reason I wanted AS3 running virtually was so I could test production multi-threaded code using redhat's 2.4 kernel with back-ported nptl. in production, the code would be using nptl but on my virtual machine, nptl would have to be disabled to get xen to work.

http://lwn.net/Articles/139964/

不能把链接和缩进整个复制过来
很多 blog 的编辑器提供很高级的复制粘贴功能例如 CU...