Messages in this thread | | | Date | Mon, 31 Aug 1998 15:07:31 +0200 | From | Alexander Kjeldaas <> | Subject | Re: Linux Interrupt Latency benchmark v4 avaible -> detected irq bottleneck before do_bottom_half() |
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On Fri, Aug 28, 1998 at 03:29:44PM +0200, Andrea Arcangeli wrote: > > With an hacked version of lil + patch-ikd with kernel tracer enabled I > exactly discovered what is stalling the irq. It' s the timer irq. > [...] > > So I think there' s really no way to reduce the maximal irq latency (that > happens meanly _once_ after a continuous train of 200000 irq). I don' t > think it' s a good idea to allow the timer interrupt to run with interrupt > enabled.... A _maximal_ latency of ~2557 cycles on a 166Mhz P5noMMX > (15,4uSec) is a very good time I think though... ;-). The mean is 5usec on > the same hardware. >
Hmm.. QNX guarantees 5us latency on a P133 so there _must_ be a way for us to do better than 20us.
Btw, I ran your module (v3) for 14 hours on a PII233 and got 3.9us min and 20.3max. The mean calculated by the module couldn't be trusted because of the integer arithmetic, but from other tests with fewer interrupts, I think it's very close to the minimum time.
astor
-- Alexander Kjeldaas, Guardian Networks AS, Trondheim, Norway http://www.guardian.no/
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