Messages in this thread | | | Date | Thu, 21 Jan 1999 14:11:15 -0600 (CST) | From | Oliver Xymoron <> | Subject | Re: Linux Kernel constraints! |
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On Thu, 21 Jan 1999, Yogesh Bansal wrote:
> Recently(dec.) in WindowsNT magazine comparisons/similarities between > various flavours of unix and nt had come. In the same article Linux was > ignored as enterprise os on account of following kernel 'limitations' : > > 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.
> 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.
> 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.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."
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