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interrupt latency

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interrupt latency

Postby Phungte » Mon Feb 14, 2005 6:11 pm

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
Phungte
 

Re: interrupt latency

Postby Mario Charest » Mon Feb 14, 2005 11:43 pm

"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

Mario Charest
 

Re: interrupt latency

Postby rgallen » Fri Feb 18, 2005 11:44 pm

Mario Charest wrote:"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



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....
rgallen
QNX Master
 
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