Messages in this thread | | | Date | Thu, 21 Jan 1999 22:45:42 -0500 (EST) | From | Alexander Viro <> | Subject | Re: Linux Kernel constraints! |
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On Thu, 21 Jan 1999, Oliver Xymoron wrote:
> 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.
by bottom half. Looks like the author means hard RT stuff.
> > 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.
kernel_lock is still there. It's held by all filesystem-related syscalls. dcache is still not SMP-safe. Ditto for struct file -related operations.
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