It seems like those who already have monolithic kernel and 'aspiring' to have different privelege level at different stages uses the term hybrid (may be like core kernel and some drivers in kernel space) but not pure micro kernel. All the things that are not perfect is good in this world :) so those don't fall under strict definitions of monolithic and micro kernel is hybrid and is good.
Thanks, -Bijoy On 6/5/08, Jain Johny <jainmjo at gmail.com> wrote: > 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 > _______________________________________________ > Mailinglist mailing list > Mailinglist at ilug-cochin.org > http://ilug-cochin.org/mailman/listinfo/mailinglist_ilug-cochin.org > >
