Saturday November 8, I received an email from someone, inquiring if I would be interested in "doing a first interview/introduction into a new operating system". We get these emails and news submissions all the time, and most of the time, "new operating system" means Ubuntu-with-a-black-theme, so we don't bother. I figured this time things wouldn't be different, but after a bit of digging around, there's a little more to it this time.
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Member since:2006-01-24
poundsmack wrote:
-"and utalizes (at least on intel) multi core CPU's better than linux currently ( as up 2.6.27.5 ) as i have and develop for both. this has actualy promted me to do a bench marking of the 2 systems, both in just kernel and text mode, as well as light weight GIU's (linux with something like fluxbox, and QNX with photon)."
Well, the link was pretty pointless as it contained no comparison whatsoever. Also, while it's good that you have benchmarked it, a total lack of data aswell as how you've benchmarked them makes the statement pretty pointless and lumps it together with all the other subjective 'it feels faster' nonsense scattered across the web. By design, monolithic kernels should be faster than microkernels, is anyone disputing this? There are advantages with running everything in it's own process (stability being number one, modularity also comes to mind), but speed is not one of them. In a monolithic kernel the system call cost is setting and resetting the supervisor bit, and no overhead at all once in kernel space where all memory is accessable. In a microkernel you have to pass messages through the kernel out to different processes and they again have to respond through the same message mechanism which is alot slower than accessing process memory directly.
Now one can certainly question just how much this overhead is actually costing (I know there has been alot of improvement in the messaging and context switching which should help lower the speed penalty), and this is where some up-to-date hard data benchmarks would come in handy.
AFAIK most kernel's today that employ micro-kernel characteristics are so-called 'hybrid' kernels which uses ideas from both microkernels and monolithic kernels. Haiku (my favourite OS project uses a hybrid kernel where hardware drivers and (I think) the filesystem runs in kernel space (and thus can potentially crash the system), just like they can in a monolithic kernel. Personally I prefer speed over the chance that a buggy driver may cause havoc. If my system goes down due to a buggy driver, I will blame the buggy driver, not the system. If this happened to me often then maybe I'd sing another tune, but I seriously can't remember when I last had a system crash which was related to hardware/driver malfunction. Of course if the system were somehow responsible for keeping me alive or some such, then I'd probably go with maximum stability 
Member since:2006-03-28
I am surely not expert in the OS internals area, but here's some possible parameters to consider:
1) "monolithic kernel sucks" is general attitude of many ppl, myself included, and you can't do anything about it :-) (you know, Amigan, message based system)
2) now really - what was interesting, was back then, when Amiga under the Gateway wings, was supposed to use QNX as a base for new OS. I remember when Linus joined the message board, with some claims, and as fast as he joined he left, because real gurus were there - with QNX. You could see many ppl claiming, that QNX had some 20-30 (micro?) sec latency, whereas Linux, at that time, some 600? Well, it was in 1997/8? I do remember Dave Haynie (one of Amiga designers) stating something like Linux was not at all usable for things like multimedia, e.g. sound, like BeOS was at that time - just because of latency. So - why had it so bad latency, while being monolithic? I suppose nowadays, the issue with latency is gone, and who knows, maybe my understanding of the issue is not correct anyway ...
Member since:2005-07-13
"Also, while it's good that you have benchmarked it, a total lack of data aswell as how you've benchmarked them makes the statement pretty pointless and lumps it together with all the other subjective 'it feels faster' nonsense scattered across the web."
by "prompted me to do a benchmark, it means i havent done one officialy yet but due to this I will be doing on, and it will be fairly extensive. I will likely do it this weekend when i get time.
Member since:
2005-07-13
while there are tons of QNX vs LInux articles i could fine, none of them were comapiring QNX to the 2.6 linux kernel so I chose this one, ( http://www.qnx.com/news/pr_2870_1.html ).
I can verify this is correct that QNX can boot in a few seconds and is lightning quick and utalizes (at least on intel) multi core CPU's better than linux currently ( as up 2.6.27.5 ) as i have and develop for both. this has actualy promted me to do a bench marking of the 2 systems, both in just kernel and text mode, as well as light weight GIU's (linux with something like fluxbox, and QNX with photon).
but as someone who uses embeded version of QNX and linux daily i can honestly say QNX is faster in boot, alication load, and data write to the file system. as far as apication usage and responsiveness, well that usualy depends on the app, so it's a toss up.
Edited 2008-11-11 16:28 UTC