Re: Timer Interrupts, please CC hamilton@sedsystems.ca

[George Anzinger <george@mvista.com>]

Kendrick Hamilton wrote:
> Hello,
>    Please send/cc responses to hamilton@sedsystems.ca
>    We are using a custom modulator card with the Linux 2.2.16 kernel 
> running on an IBM e-server (dual 2.8GHz, a lot of RAM). The modulator 
> card uses interrupts to send data (the card has a large FIFO and 
> interrupts when almost empty). The interrupt service routine re-fills 
> the fifo. While it is re-filling the FIFO interrupts are disabled. We 
> are noticing horrible clock skew.
>    Can you tell me the frequency of timer interrupts used by the linux 
> 2.2.16 kernel on Intel x86 SMP platform. I want to know how long my 
> interrupt service routine can leave the interrupt disabled.

Two VERY different questions IMNSHO. :)

The normal tick time for the x86 platform on 2.4.x kernels was/is 
10ms.  The interrupt latency, on the other hand, is usually well under 
1ms.  Shame to see that go up.



-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml