Messages in this thread | | | From | "pleXus" <> | Subject | [OFFTOPIC] Re: Linux Kernel constraints! | Date | Sat, 23 Jan 1999 02:56:59 -0700 |
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>On Thu, 21 Jan 1999, Yogesh Bansal wrote: > >> 1. kernel is not preemptive. ie even a higher priority user thread cant >> cause another thread to be swapped if the other thread is presently running >> in privileged/kernel context. > >Not true. All things that are not running with interrupts disabled can be >preempted. >
Ahem. This is referring (in BOTH instances) to process/thread level. No 'thread' can. if you want to include via hooking an interrupt so be it, but don't you think that's a little beyond the argument on either system?
>> 2. kernel is not reentrant. ie.only one thread in kernel context at a time. > >Pfft. This is absurd. Every process that is blocked on I/O is _in kernel >context_. This is the way UNIX works. >
Pfft.. Oh dear, it's been weeks since I laughed. I think this was referring to re-entrancy of and in the kernel.
>> 3. kernel is not multi processing in the sense that on multiprocessor >> systems it will run on only one cpu at a time. > >And this is even more absurd. SMP is _symmetric_. Kernel runs on all >processors _by definition_. There may be some confusion here with respect >to lock granularity though. The very first SMP kernels had a single lock >that protected most data structures, which drastically limited kernel >concurrency. Current kernels have more fine-grained locking that allow >much better concurrency and therefore better scaling.
Can someone more knowledgeable explain to me whether or not the KERNEL runs on more than one processor.. I am curious, because that would be interesting to hear.
- ely
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