Timer Interrupts, please CC hamilton@sedsystems.ca

Timer Interrupts, please CC hamilton@sedsystems.ca

[Kendrick Hamilton]

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.
    TIA
Kendrick Hamilton
hamilton@sedsystems.ca

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

[George Anzinger]

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