"call-gate" should be "task-gate" here.
> 2) I don't see the connection between kernel entry and TSS based task
> switch.
The task switch is implemented by selecting a Tassk Gate descriptor in
either the GDT or the LDT.
See:
Protected Mode Software Architecture
Tom Shanley
MindShare, Inc.
ISBN: 0-201-55447-X
Chapter 11: Mechanics of a Task Switch
> Mingo already has patches that replace the current TSS method
> with software based context switchs.
Good. When these changes have been integrated into the mainstream
releases, Linux will be as fast as FreeBSD in this regard. Which is
beside the main point, that is that you can ask the question as many
ways as you want, kernel threading is still a loss for everything
but SMP, and not a loss there only under specific conditions, which
neither Linux nor FreeBSD can provide at this time.
> 3) I'm not sure about Terrys definition of "efficient", but if he means
> required CPU cycles I thought that there were not that many left in
> Linux that FreeBSD could be better. Has anybody hard numbers for both
> kernels?
CPU cycles and cache line invalidation, both.
Note that FreeBSD does similar things, but only when running a VM86()
task, so the overhead is not constant.
Terry Lambert
terry@lambert.org
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