An interesting project I ran across, it started in 2004.
From http://vcl.ncsu.edu/:
The Virtual Computing Lab (VCL) is a remote access service that allows you to reserve a computer with a desired set of applications for yourself, and remotely access it over the Internet.
You can use all your favorite applications such as Matlab, Maple, SAS, Solidworks, and many others. Linux, Solaris and numerous Windows environments are now available to all NC State students and faculty.
Leasing custom environments to “public-ish” users via PXE or similar technology was happening in other places in 2004, but I never saw anything at this scale.
It is clear that some kind of reconfiguration/resetting happens:
What rights do I have on the VCL machine?
On custom Windows and Linux environments you have adminstrative and root level rights. Since the VCL system reloads each expired reservations with a clean environment, there is no threat of any residual data being left on a machine for the next user.
On Linux and Solaris Lab machine environments, you only have user level rights. The same premissions as you would experience at the console of a walk-in lab.
I wonder when they added the VM support mentioned at http://vcl.ncsu.edu/help/general-information/how-it-works:
The management nodes each control a subset of the VCL resources. These can be blades, virtual machines or lab machines. Currently, a set of individual blades or virtual machines can only be managed by a single management node. Typically there are anywhere from 80-120 physical computer nodes (blades) under one management node. Again the physical computer nodes can either be running a bare metal environment or a Virtual Machine hypervisor.
Here are deployment stats captured on Aug 25, 2008:
- Total blades online: 438
- Total blades offline: 87
- Active Reservations: 49
Cool.
The Ceph Distributed Network File System is an interesting, new project announced on the lkml
“Ceph is a distributed network file system designed to provide excellent performance, reliability, and scalability with POSIX semantics.”
(Note the comments at the kerneltrap link, there is an update on the GPFS part of the announcement)
In Torvalds releases 2.6.21 kernel, Steven J. Vaughan-Nichols reports at length on the 2.6.21 kernel’s clockevents and dyntick (dynamic ticks) patches.
The result of these merges is a uniform timekeeping/scheduling interface (clockevents) and the ability to take the CPU into a true idle state if nothing is going on, shutting down the timer event and instead waiting for a regular interrupt or a scheduled, future event (this is dynticks).
This could apparently help with virtualization scheduling:
In the future, both these features will be used to improve virtualization. The virtualization manager — rather than scheduling by HZ — will determine which program or virtual operating system should have the lion’s share of the processor’s time. This is not a pie in the sky idea. The technique was already being used with Linux on IBM mainframes years ago, when trying to deal with a thousand virtual Linux servers at once using HZ scheduling. It lead to situations where the timer interrupt overhead alone was using up almost all of the processors’ time.
I’d imagine a thousand virtual servers splitting the system at once could do that :-)
He points to this informative LWN article from February. That further explains clockevents and dynticks — but also suggests that going tickless during idle times is just the beginning for dynticks:
What’s in 2.6.21 is, thus, not a full dynamic tick implementation. Eliminating the tick during idle times is a good step forward, but there is value in getting rid of the tick while the system is running as well - especially on virtualized systems which may be sharing a host with quite a few other clients. The dynamic tick documentation file suggests that the developers have this goal in mind
Well. On to more important stuff this may promise: battery life! I am joining this LWN commenter, crossing my fingers:
I haven’t seen benchmarks on this in particular, but I remember reading a piece a while ago where a guy claimed that his laptop battery lasts TWICE as long with a 100Hz tick than with a 1000Hz tick… So, I’m expecting great things…
