From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Wed, 22 Oct 2008 09:02:13 +0200
From: Wolfgang Grandegger <wg@domain.hid>
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Subject: Re: [Xenomai-help] Reducing Kernel Mode Interrupt Latency
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To: Henry Bausley <hbausley@domain.hid>
Cc: xenomai@xenomai.org

Henry Bausley wrote:
> Is there any way the kernel mode interrupt handling maximum times can be
> decreased.  I very much need to reduce my kernel mode interrupt
> latencies.  I know my hardware is capable of better performance based
> upon measurements done with RT Linux.  Below is our timing comparison,
> all times are the maximums.
> 
> 
> Xenomai 2.4.5 interrupt handler  w/ Kernel 2.6.26 powerpc, gcc 4.2
> -------------------------------------------------------------------
> AMCC 440EP - 24.5 usec
> AMCC 460EX - 16.5 usec
> 
> 
> FSM Labs RT-Linux 2.2 w/ Kernel 2.6.14 ppc, gcc 3.3
> ---------------------------------------------------
> AMCC 440EP - 10.0 usec
> AMCC 460EX - Not Available, would require 10's of thousands of dollars
> to WindRiver

What exactly did you measure and did you run the tests under comparable
(non real-time) system load? As cache re-fills are causing significant
latencies, code size matters, but I'm surprised that the difference is
that big.

Wolfgang.