Hi Mahesh, I am also not an expert in OS design. But, I am interested in these things. (I really loved reading Tanenbaum-Torvalds debate. :-) A couple of years ago.) I am reading the posts in realworldtech.com. It will take a long time. :-)
The more wiki I read, the more confused I become. :-( I just read that XNU is monolithic kernel based on Mach(which is microkernel). So, is it hybrid or monolithic? GNU Hurd is based on GNU Mach. I "think" its a pure implementation of micro kernel. I am sure that micro and hybrid cant scale as much as monolithic. But for PCs and low end servers, it serves the purpose. In a good hybrid design, the whole kernel shouldnt fail when one of the subsystem fails. But it happens in NT. So, I think the NT implementation is not good. PS:I dont use email license. Its Shirish who uses it. And I am for the first time seeing a email license. What is the use of it? Can't copy text (and send to others) from licensed email? :-) On Thu, Jun 5, 2008 at 3:36 PM, Mahesh Aravind <ra_mahesh at yahoo.com> wrote: > Jain, > > --- On Thu, 6/5/08, Jain Johny <jainmjo at gmail.com> wrote: > > > I have read that wiki page. There is nothing in it. It says > > *"Many operating > > systems and kernel experts (incl. Torvalds and Rao) have > > dismissed the label > > as meaningless, and just marketing"*. Does it mean > > that hybrid kernels are > > bad? I don't think so. > > They call it bad, because from the point of view of a comp. scientist, it's > hard to maintain, difficult to debug and maintain, and the design is flawed. > Microkernel advocates support because "design"-wise it's superior, very > secure, and fuctionally surpassing the monolithic ones. > > Hybrid -- yeah, seems like a Marketing term -- like cars. Both petrol AND > CNG. But UNIX philosophy says (40yrs old OS design) simple things work > most. That's why microkernels are hard to write. > > Besides, having the "servers" in kernel space makes them very easy to > exploit -- you can't do that in micro-kernel ones. Servers are in userspace > and memory protection is very strict. Think modern Linux systems here: > kernel rootkits! > > Hybrid (if you dare use the term) technically one of the either (monolithic > or micro) kernels with features of the other added. linux 2.6 and above are > essentially hybrid, if you look at it -- technically. But since IPC, GUI > handling, process handling (init) etc are handled in user-space, I don't > think anyone calls it hybrid. > > If you look at it from "good and bad" side -- there's bad to everything. > but if it solves the problem, that you're wanting it to solve. It's good. > > > > > Doesn't NT kernel serves the purpose for Windows? > Yeah, it's purpose is to proliferate viruii. > > > Doesn't XNU kernel serves the purpose for Mac OS X? > > Darwin? yes. But Apple is a niche OS. Think of Apple being deployed as a > server? Can it scale? Can it handle load? Can it multi-task? threads? > clustering? > > Inferno is a distributed OS -- it scales. > > > > > The "loadable kernel modules" and > > "fuse" in Linux are actually Micro kernel > > features. Right? The monolithic Linux kernel also has now a > > kind of hybrid > > design. > It's hybrid -- technically. But is there a "standard" to compare against, > and to label it as "OK, it satisfies the said features -- let's call it > hybrid". > > We need someone with both OS research and OS writing background to decide > authoritatively about the "goodness" and "badness" of kernel design. I am > neither. > > But as I said. Designs are built to satisfy, and rectify one problem. > That doesn't make it the be-all and end-all of "Good, clean, ideal" kernel > design. > > See this link: > http://www.realworldtech.com/forums/index.cfm?action=detail&id=66595&threadid=66595&roomid=2 > > click on "Next post >>>" to read through various mails in the thread. > That's experts discussing the issue. Might throw some light. > > In the mean time, search "Is hybrid kernels good?" in scholar.google.com-- it > does bring out something. > > No worries, > > Mahesh Aravind. > ----- > PS: I see that you've taken out your "license". Good! > > > > -- Regards, Jain M Johny jainmjo[at]gmail -------------- next part -------------- An HTML attachment was scrubbed... URL: http://ilug-cochin.org/pipermail/mailinglist_ilug-cochin.org/attachments/20080605/83ea991b/attachment.html
