interrupt latency

QNX Newsgroups (Archives) qnx.evaluation
1

Hi all,

I am running an interrupt latency test on Momentics 6.3, on a 2.4GHz P4,
using a PCI board. The PCI board sits on a 66MHz bus.
A logic analyser is connected to the bus and gives the timing of the
latency.

The numbers I got was:
. from hardware interrupt to interrupt handler (the routine given to
InterruptAttach): ~10uSecs.
. from interrupt handler to interrupt thread (the routine calling
InterruptWait): ~20uSecs.

Can you please let me know if these numbers are reasonable, most often
seen… Or I did something wrong.

Thanks for your comments.

Phungte

2

“Phungte” <phungte@decru.com> wrote in message
news:cuqp89$8r7$1@inn.qnx.com…

Hi all,

I am running an interrupt latency test on Momentics 6.3, on a 2.4GHz P4,
using a PCI board. The PCI board sits on a 66MHz bus.
A logic analyser is connected to the bus and gives the timing of the
latency.

The numbers I got was:
. from hardware interrupt to interrupt handler (the routine given to
InterruptAttach): ~10uSecs.
. from interrupt handler to interrupt thread (the routine calling
InterruptWait): ~20uSecs.

Yeah these number look a bit high (gut feeling), is the interrupt shared?

Can you please let me know if these numbers are reasonable, most often
seen… Or I did something wrong.

Thanks for your comments.

Phungte

3

Mario Charestwrote:
“Phungte” <> phungte@decru.com> > wrote in message
news:cuqp89$8r7$> 1@inn.qnx.com> …
Hi all,

I am running an interrupt latency test on Momentics 6.3, on a 2.4GHz
P4,
using a PCI board. The PCI board sits on a 66MHz bus.
A logic analyser is connected to the bus and gives the timing of
the
latency.

The numbers I got was:
. from hardware interrupt to interrupt handler (the routine given
to
InterruptAttach): ~10uSecs.
. from interrupt handler to interrupt thread (the routine calling
InterruptWait): ~20uSecs.

Yeah these number look a bit high (gut feeling), is the interrupt
shared?

Can you please let me know if these numbers are reasonable, most
often
seen… Or I did something wrong.

Thanks for your comments.

Phungte

[/quote:1100fface3]

Yeah, on a 2.4Ghz P4, I would expect those numbers to be expressed in
nanoseconds rather than microseconds. I remember getting 5 usec
latency on a P100 (IRQ → interrupt handler) way back when a P100
was a decent machine…