IRQ latency (was Re: RTEMS-MVME5500 BSP v1.3 available)

[Peter Dufault]

On Aug 10, 2005, at 8:36 PM, Kate Feng wrote:


>
> Peter Dufault  wrote :
>
>
>
>> Me? No, I *never* disable interrupts! (well, almost never).
>>
>>
>
> Yes, it's better to limit it to the minimum.
>
>
>
>> But seriously, no I didn't disable interrupts. I'm a firm believer in
>> lock-free systems, which to my thinking means trying to push the
>> locks down to the hardware level.
>>
>>
>
> I  am not sure  if you will get an  accurate timestamp in you test as
> you mention  that you use  system clock, especially  under the heavy
> load.   Anyway,  Till should make a  conclusion about  its pedigree.
> He is the one who made the enhancement  in RTEMS4.7 PPC
> shared port.
>
>
>

Kate asked me off-list if I'd disabled interrupts in my timings, and  
this is how I responded.  I'd have been less tongue-in-cheek on-list,  
but it's OK with me for anyone forward my emails unless I say not to.

I use the 64-bit Power-PC time counter, not the system clock, so the  
timings should be very accurate.

In an earlier posting I said that if something resets that time  
counter I'm in trouble, but I'm 99.99% sure that the time counter is  
left alone.

Till will tell.

Peter