Messages in this thread | | | Date | Fri, 11 Feb 2000 17:07:00 -0700 | From | yodaiken@chelm ... | Subject | Re: latest 'guaranteed low latency' patch against 2.2.14 |
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On Tue, Feb 08, 2000 at 10:32:01PM +0100, Ingo Molnar wrote: > yep, completely agreed. Nevertheless there is a new method you might not > have heard about: the IOAPIC-based NMI watchdog i developed about a year > ago and which got added recently to the 2.3 SMP code. The NMI watchdog > also provides easy access to microsecond-resolution excuted (kernel level) > code - on standard PC (SMP) hardware. No kernel change is necessery, it's > part of the standard kernel. NMI interrupts are the 'secret backdoor' to > the PC architecture to guarantee hard-RT-latencies, even if the OS does > not directly support low latencies. > > any device interrupt can be turned into an NMI interrupt - of course > special handlers have to be written, and careful coding is needed as no > other kernel facilities can be relied on.
This is an intrinsically terrible idea 1. It creates drivers that are x86+IOAPIC specific 2. It creates bizzare kernel bugs that will be impossible to track 3. It creates a disgusting overhead in figuring out what nmi corresponds to what irq. 4. It will make drivers fail with RTLinux . Of course they will be idiotic drivers, but ...
> > -- mingo > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.tux.org/lkml/
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
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