By: _Arthur (Arthur_.delete@this.sympatico.ca), May 9, 2006 7:06 am
Room: Moderated Discussions
I found that distinction between microkernels and "monolithic" kernels useful:
With microkernels, when you call a system service, a "message" is generated to be handled by the kernel *task*, to be dispatched to the proper handler (task).
There is likely to be at least 2 levels of task-switching (and ring-level switching) in a microkernel call.
With a monokernel call, the call is identical to a library function call. Theres an implicit priority level change when you call the kernel, but it is still your user-level process running, exactly as if it was a library call.
Changes of priority levels used to be a very expensive operation, 150+ clocks for the CALL gate instruction alone, on a 386. In current processors such priority level switch costs are greatly reduced.
With a monolithic kernel, there will be the priority level switch, but then no additional cost other than the normal code to service your call.
With a micro-kernel, you have to fill a message structure, context switch to activate the kernel task, dispatch the call, context-switch to the proper handler task again, who then do the required system service, but which may entail further message-passing for ancillary system calls to other handlers, like requesting a memory buffer. You can then return to the caller process with a completion of its request.
So the machinery to handle system calls tends to be significantly heavier for Microkernels. This is balanced by a much smaller kernel proper (less likely to contain bugs), and the capacity to keep on running if a handler (driver) fails.
With microkernels, when you call a system service, a "message" is generated to be handled by the kernel *task*, to be dispatched to the proper handler (task).
There is likely to be at least 2 levels of task-switching (and ring-level switching) in a microkernel call.
With a monokernel call, the call is identical to a library function call. Theres an implicit priority level change when you call the kernel, but it is still your user-level process running, exactly as if it was a library call.
Changes of priority levels used to be a very expensive operation, 150+ clocks for the CALL gate instruction alone, on a 386. In current processors such priority level switch costs are greatly reduced.
With a monolithic kernel, there will be the priority level switch, but then no additional cost other than the normal code to service your call.
With a micro-kernel, you have to fill a message structure, context switch to activate the kernel task, dispatch the call, context-switch to the proper handler task again, who then do the required system service, but which may entail further message-passing for ancillary system calls to other handlers, like requesting a memory buffer. You can then return to the caller process with a completion of its request.
So the machinery to handle system calls tends to be significantly heavier for Microkernels. This is balanced by a much smaller kernel proper (less likely to contain bugs), and the capacity to keep on running if a handler (driver) fails.
Topic | Posted By | Date |
---|---|---|
Hybrid (micro)kernels | Tzvetan Mikov | 2006/05/08 04:41 PM |
Hybrid (micro)kernels | S. Rao | 2006/05/08 06:14 PM |
Hybrid (micro)kernels | Bill Todd | 2006/05/08 06:16 PM |
Hybrid (micro)kernels | Tzvetan Mikov | 2006/05/08 07:21 PM |
Hybrid (micro)kernels | nick | 2006/05/08 07:50 PM |
Hybrid (micro)kernels | Bill Todd | 2006/05/09 01:26 AM |
There aren't enough words... | Rob Thorpe | 2006/05/09 02:39 AM |
There aren't enough words... | Tzvetan Mikov | 2006/05/09 03:10 PM |
There aren't enough words... | Rob Thorpe | 2006/05/15 12:25 AM |
Hybrid (micro)kernels | Tzvetan Mikov | 2006/05/09 11:17 AM |
Hybrid (micro)kernels | Bill Todd | 2006/05/09 04:05 PM |
Hybrid (micro)kernels | rwessel | 2006/05/08 11:23 PM |
Hybrid kernel, not NT | Richard Urich | 2006/05/09 06:03 AM |
Hybrid kernel, not NT | _Arthur | 2006/05/09 07:06 AM |
Hybrid kernel, not NT | Rob Thorpe | 2006/05/09 07:40 AM |
Hybrid kernel, not NT | _Arthur | 2006/05/09 08:30 AM |
Hybrid kernel, not NT | Rob Thorpe | 2006/05/09 09:07 AM |
Hybrid kernel, not NT | _Arthur | 2006/05/09 09:36 AM |
Linux vs MacOSX peformance, debunked | _Arthur | 2006/05/18 07:30 AM |
Linux vs MacOSX peformance, debunked | Rob Thorpe | 2006/05/18 08:19 AM |
Linux vs MacOSX peformance, debunked | Anonymous | 2006/05/18 12:31 PM |
Hybrid kernel, not NT | Linus Torvalds | 2006/05/09 08:16 AM |
Hybrid kernel, not NT | Andi Kleen | 2006/05/09 02:32 PM |
Hybrid kernel, not NT | myself | 2006/05/09 03:24 PM |
Hybrid kernel, not NT | myself | 2006/05/09 03:41 PM |
Hybrid kernel, not NT | Brendan | 2006/05/09 05:26 PM |
Hybrid kernel, not NT | Linus Torvalds | 2006/05/09 08:06 PM |
Hybrid kernel, not NT | Brendan | 2006/05/13 01:35 AM |
Hybrid kernel, not NT | nick | 2006/05/13 04:40 AM |
Hybrid kernel, not NT | Brendan | 2006/05/13 09:48 AM |
Hybrid kernel, not NT | nick | 2006/05/13 07:41 PM |
Hybrid kernel, not NT | Brendan | 2006/05/13 09:51 PM |
Hybrid kernel, not NT | nick | 2006/05/14 05:57 PM |
Hybrid kernel, not NT | Brendan | 2006/05/14 10:40 PM |
Hybrid kernel, not NT | nick | 2006/05/14 11:46 PM |
Hybrid kernel, not NT | Brendan | 2006/05/15 04:00 AM |
Hybrid kernel, not NT | rwessel | 2006/05/15 07:21 AM |
Hybrid kernel, not NT | Brendan | 2006/05/15 08:55 AM |
Hybrid kernel, not NT | Linus Torvalds | 2006/05/15 09:49 AM |
Hybrid kernel, not NT | nick | 2006/05/15 04:41 PM |
Hybrid kernel, not NT | tony roth | 2008/01/31 02:20 PM |
Hybrid kernel, not NT | nick | 2006/05/15 06:33 PM |
Hybrid kernel, not NT | Brendan | 2006/05/16 01:39 AM |
Hybrid kernel, not NT | nick | 2006/05/16 02:53 AM |
Hybrid kernel, not NT | Brendan | 2006/05/16 05:37 AM |
Hybrid kernel, not NT | Anonymous | 2008/05/01 10:31 PM |
Following the structure of the tree | Michael S | 2008/05/02 04:19 AM |
Following the structure of the tree | Dean Kent | 2008/05/02 05:31 AM |
Following the structure of the tree | Michael S | 2008/05/02 06:02 AM |
Following the structure of the tree | David W. Hess | 2008/05/02 06:48 AM |
Following the structure of the tree | Dean Kent | 2008/05/02 09:14 AM |
Following the structure of the tree | David W. Hess | 2008/05/02 10:05 AM |
LOL! | Dean Kent | 2008/05/02 10:33 AM |
Following the structure of the tree | anonymous | 2008/05/02 03:04 PM |
Following the structure of the tree | Dean Kent | 2008/05/02 07:52 PM |
Following the structure of the tree | Foo_ | 2008/05/03 02:01 AM |
Following the structure of the tree | David W. Hess | 2008/05/03 06:54 AM |
Following the structure of the tree | Dean Kent | 2008/05/03 10:06 AM |
Following the structure of the tree | Foo_ | 2008/05/04 01:06 AM |
Following the structure of the tree | Michael S | 2008/05/04 01:22 AM |
Hybrid kernel, not NT | Linus Torvalds | 2006/05/09 05:19 PM |
Microkernel Vs Monolithic Kernel | Kernel_Protector | 2006/05/09 09:41 PM |
Microkernel Vs Monolithic Kernel | David Kanter | 2006/05/09 10:30 PM |
Sigh, Stand back, its slashdotting time. (NT) | Anonymous | 2006/05/09 10:44 PM |
Microkernel Vs Monolithic Kernel | blah | 2006/05/12 08:58 PM |
Microkernel Vs Monolithic Kernel | Rob Thorpe | 2006/05/15 01:41 AM |
Hybrid kernel, not NT | AnalGuy | 2006/05/16 03:10 AM |
Theory versus practice | David Kanter | 2006/05/16 12:55 PM |
Distributed algorithms | Rob Thorpe | 2006/05/17 12:53 AM |
Theory versus practice | Howard Chu | 2006/05/17 02:54 AM |
Theory versus practice | JS | 2006/05/17 04:29 AM |
Play online poker, blackjack !!! | Gamezonex | 2007/08/16 01:49 PM |
Hybrid kernel, not NT (NT) | atle rene mossik | 2020/12/12 09:31 AM |
Hybrid (micro)kernels | philt | 2006/05/14 09:15 PM |
Hybrid (micro)kernels | Linus Torvalds | 2006/05/15 08:20 AM |
Hybrid (micro)kernels | Linus Torvalds | 2006/05/15 11:56 AM |
Hybrid (micro)kernels | Rob Thorpe | 2006/05/16 01:22 AM |
Hybrid (micro)kernels | rwessel | 2006/05/16 11:23 AM |
Hybrid (micro)kernels | Rob Thorpe | 2006/05/17 12:43 AM |
Hybrid (micro)kernels | rwessel | 2006/05/17 01:33 AM |
Hybrid (micro)kernels | Rob Thorpe | 2006/05/19 07:51 AM |
Hybrid (micro)kernels | rwessel | 2006/05/19 12:27 PM |
Hybrid (micro)kernels | techIperson | 2006/05/15 01:25 PM |
Hybrid (micro)kernels | mas | 2006/05/15 05:17 PM |
Hybrid (micro)kernels | Linus Torvalds | 2006/05/15 05:39 PM |
Hybrid (micro)kernels | Colonel Kernel | 2006/05/15 09:17 PM |
Hybrid (micro)kernels | Wink Saville | 2006/05/15 10:31 PM |
Hybrid (micro)kernels | Linus Torvalds | 2006/05/16 10:08 AM |
Hybrid (micro)kernels | Wink Saville | 2006/05/16 09:55 PM |
Hybrid (micro)kernels | rwessel | 2006/05/16 11:31 AM |
Hybrid (micro)kernels | Linus Torvalds | 2006/05/16 12:00 PM |
Hybrid (micro)kernels | Brendan | 2006/05/16 01:36 AM |
Hybrid (micro)kernels | Paul Elliott | 2006/09/03 08:44 AM |
Hybrid (micro)kernels | Rob Thorpe | 2006/09/04 09:25 AM |
Hybrid (micro)kernels | philt | 2006/05/16 12:55 AM |
Hybrid (micro)kernels | pgerassi | 2007/08/16 07:41 PM |
Another questionable entry on Wikipedia? | Chung Leong | 2006/05/18 10:33 AM |
Hybrid (micro)kernels | israel | 2006/05/20 04:25 AM |
Hybrid (micro)kernels | Rob Thorpe | 2006/05/22 08:35 AM |