Re: v2.3.17pre1 - Patches, Complaints, Questions and Jubilations

Andrea Arcangeli (andrea@suse.de)
Thu, 9 Sep 1999 01:56:52 +0200 (CEST)


On Mon, 6 Sep 1999, Linus Torvalds wrote:

>The SMP automatic deadlock detection parts of the IKD are extremely
>simple, impact none of the mainline code, and are occasionally very
>useful.

There are many kind of automatic deadlock detection in the ikd patch. I
believe you are talking about the IO-APIC-NMI_WATCHDOG from Ingo, since
it's the only one that may run on a serious production envinroment as a
default thing.

But the NMI patch has a performance-downside too: the timer irq will be
driven from the 8259 and not from the apic chip (the io-apic will instead
run an NMI irq for the same hardware-event), and that means all timer irq
handlers will be run on the first CPU and so the kernel will scale worse
(the other CPU may be idle at the same time).

So if you want it into the stock kernel I am fine with it, but I believe
it's not a good idea to make it a default thing.

Andrea

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