On Wed, Sep 02, 1998 at 03:27:15AM -0500, Manoj Apte wrote:
>
> > > in a handler). I created my own fast handler registered at IRQ32 (
> > > interrupt is generated by
> > > the APIC timer on a Ppro 200) that gives me a latency of approx 2300
> > > nanoseconds
> >
> > the APIC timer interrupt is a CPU-internal IRQ, and thus has lower
> > latencies. It should have identical latencies to a software interrupt.
> > (like your numbers show). I measured 500 cycles _total_ profiling
> > interrupt cost. This makes it possible to run 100 thousand IRQs a second
> > profiling on a 100MHz P5. (i've tried it. It's noticeable but it works)
> >
>
> Agreed.. but my question was about why i see periodic mega-latencies of
> the order of 15us every 30 seconds or so. I want to track the source of
> this, so that _if_ i can dsiable that probelm, I have a much more
> predictable APIC interrupt latency.
>
> > _external_ interrupts have much higher latencies. (especially as old
> > XT-PIC interrupts halt the CPU for a considerable amount of time ... this
> > is not the case with IO-APIC and inter-CPU interrupts.)
> >
> > -- mingo
> >
>
>
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----------------------------------- Victor Yodaiken Department of Computer Science New Mexico Institute of Mining and Technology Socorro NM 87801 Homepage http://www.cs.nmt.edu/~yodaiken PowerPC Linux page http://linuxppc.cs.nmt.edu Real-Time Page http://rtlinux.org
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