Slashdot Mirror
Plex86 Lives, As Lightweight VM Technology
Kevin P. Lawton writes "Plex86 has been completely overhauled, and simplified to be a user (application) code only Virtual Machine technology. For running user code, many of the heavy weight x86-VM techniques are unnecessary. But the bonus is, Linux can easily be made to run inside the plex86 VM, so that the kernel is actually 'pushed down' to user privilege level. This has been demonstrated on both Linux 2.4 and 2.5 kernels. Thus, Linux can run in a plex86 VM without the need for any heavy virtualization. My goal is to keep the code base trim, tight, auditable and get to usable releases quickly. And to favor those goals over adding unnecessary complexities. The first milestones have just been reached, so it's still early in development. There are email lists available on the main plex86 site."
A topic brought up on Slashdot some time ago had some interesting discussion that if Free solutions like Plex86 took off, it would destroy VMWare's business model, and show other businesses that you can't make money developing software for Linux because someone will undercut you with a Free solution. How do you respond to these fears?
Funny you should ask. The site talks about using the new plex86 as an acceleration engine for Bochs. So, instead of emulating each x86 instruction, Bochs could leverage Plex86 and get a big 'ole speedboost.
Kevin's posted a very limited test case demonstrating this ability to the Bochs lists a bit ago.
Breakfast served all day!
There are two things I would like to do with plex86:
0) multiple virtual Linux servers, each in its own chroot jail.
1) run Win98 under Linux, to be able to run Win32 apps for testing purposes or backwards compatability.
Sounds like it will do multiple Linux servers very well, soon. But do they still have any hopes for plex86 running non-Linux OSes as guests?
P.S. According to reviews I have read, Win4Lin does a decent job of letting you run Win98 under Linux. It's not free software, of course.
steveha
lf(1): it's like ls(1) but sorts filenames by extension, tersely
With the changes he's made in the goals of Plex86, it sure seems as if he's targetting the same approach currently in use by User-Mode Linux. I understand it may be quite different under the hood, but will that matter to users? It doesn't matter much to me if the task is accomplished using a ptrace thread under kernel system calls or actually virtualizes hardware -- if I can run several virtual GNU/Linux systems on top of one physical system, at a reasonable speed for the load, using free software as much as possible, I'm happy. The technical details of how it's done are irrelevant to me -- what matters is the result.
If the Bochs/Plex86 combination is actually faster than Bochs by itself on X86 hardware, and can approach the speed of VMWare, well, that sounds interesting to me. Virtualization technology is a large and growing market, funding a lot of IBM's recent growth in the mid-range server market with quad and 8-processor systems running VMWare to aggregate systems, improve manageability, and reduce personnel management costs. There's no denying the need is there; VMWare posted their first profit ever last quarter because of these strong sales, with more big money coming down the pipe.
Competition among free software projects is a good thing. I'm glad to see Plex86 come out with something new that may work better than the old. But what most people wanted was to run multiple copies of Microsoft Windows on top of Linux, or to run MS Windows in VMs alongside GNU/Linux, and if that doesn't work easily & quickly, it may be a potent obstacle to widespread adoption.
Matthew P. Barnson
I learn what I think when I read what I write
Yes, but UML uses almost 80% of the processor's MTRR registers as a scratchpad to save state. Therefore, any kernel drivers that require real-time interrupt service (NET, SCSI) have to use cut-through emulation, instead of the much faster native emulation.
The bottom line is UML works fine, and exhibits quite decent responsiveness, until you start trying to push disk and or network I/O.
It's a fundemental flaw of UML. But UML's proponents consider it a necessary evil in the name of portability and lightweight robustness. I'm not sure I disagree with them.
Isn't this the same argument thrown against Mozilla a year or two ago? "It's taking to long so it isn't worth the effort." or "We have Internet Explorer anyway - why do we need another browser?"
:)
Software, especially good software, takes a lot of time to produce. Anyone can throw off crappy code quickly but to make something you'll be able to keep secure and stable over it's lifetime takes time and effort. Unless you're the developer what do you care how the effort is being spent? it's not your time or effort so feel free to go about your business doing something you feel your efforts are more useful in.
As for me I find Plex86 interesting because I don't want to spend a fortune on hardware but sometimes I do like to have a sandbox enviroment to run development stuff, test apps, or just open questionable email attachments. Bochs is to slow to run many apps properly and if I was going to spend the money for faster hardware I might as well just buy new computers. It makes more sense to use a virtualized enviroment and save some money (and hassle).
Virtualization may not have as many users as web browsers but it's technology which for the most part will continue to be useful for a long time. The x86 processor has a long history of compatible code so there is no reason to think Plex86/Bochs won't still be useful a decade from now.
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
Dude, chill out. I'd like to see your resume before you knock one of the sharpest VM programmers in the business. Not only is Kevin smart, but he knows the x86 ISA better than most people know how to read. Add on the fact that he pumps out code at an insane rate, and you get a programmer I'm grateful is working in the OSS world. Kevin's given us a lot and I'm more willing to forgive him for being a triffle distractable in exchange. People have called Kevin a lot of things (erratic, drasticable, incapable of proper commenting), but to call him shit is unbelievable. Unless you're Linus or RMS, get off the man's back.
Arrggh, it's too hard.
I work for VMware. if you want to believe we've corrupted Kevin's precious bodily fluids, feel free. I don't speak for the company, and I know nothing beyond what slashdot has posted about plex86. Consider yourself disclaimed.
If I understand the story correctly, plex86 has basically surrendered. They've given up on running arbitrary supervisor level code; the Linux guests that Kevin refers to above require a patch to "fix" something the new "lean, mean" plex86 gets wrong.
If Linus is feeling even vaguely himself, he will not accept this patch. Ordinarily, people trying to put stuff into the kernel that a) hurts performance, and b) fixes no real problem, but c) is critical to some contrived project that seems really important to the contributor get entertainingly flamed, and then shown the door. In fact, Kevin's most likely motivation for submitting this as a Slashdot story is to marshall support for his Linux patch.
Even if Linus does accept this patch, I can guarantee you that Microsoft, the FreeBSD team, the now non-existent Be, etc., won't all be taking helpful hints from Kevin about which x86 features they may and may not use. Ergo, there is nothing interesting (either commercially or geekily) you can do with plex86; the most it can hope for is to run recent-ish Linux guests on recent-ish Linux hosts. Bestill my heart.
On the upside, maybe Kevin will stop implying that VMware stole Bochs, now that he's spent four years trying to clone our software and has finally admitted defeat.