Hello Gurus,
I have developed a PCI card which will continuously interrupt every
6ms, and it is asked that none of the interrupt should be missed.
When I tested it with my driver on my HP LH3000 net server: PIII
533+128M ram, it runs perfectly well without missing any interrupts,
at least till now.
But now, my boss asked me to give him a theoretical estimation of the
interrupt missing probability. I don’t know how to calculate it. How
could I know in the worst case, how long will it take for my card
interrupt to issue the isr routine of my driver? How to calculate the
probability?
Your help is highly appreciated.
Best regards,
Jingcao mailto:xxxxx@chinaren.com
I think there was a paper about average interrupt latency on NT systems that
was published a year or two ago. I think also that it might have been from
Intel. You should do a web search. The worst case is of course pretty horrid
and undoubtedly outside the requirement that your isr should never miss a
6ms interval. All that takes is a few concurrent interrupts at higher
priority with isrs that each consume a significant portion of the 6ms. Hmm…
perhaps the floppy disk driver would do it? NT is not a real time system,
and you have little or no control over the priority of your isr.
-----Original Message-----
From: Jingcao Hu [mailto:xxxxx@chinaren.com]
Sent: Tuesday, May 23, 2000 3:04 AM
To: NT Developers Interest List
Subject: [ntdev] Question about the real time response!!!
Hello Gurus,
I have developed a PCI card which will continuously interrupt every
6ms, and it is asked that none of the interrupt should be missed.
When I tested it with my driver on my HP LH3000 net server: PIII
533+128M ram, it runs perfectly well without missing any interrupts,
at least till now.
But now, my boss asked me to give him a theoretical estimation of the
interrupt missing probability. I don’t know how to calculate it. How
could I know in the worst case, how long will it take for my card
interrupt to issue the isr routine of my driver? How to calculate the
probability?
Your help is highly appreciated.
Best regards,
Jingcao mailto:xxxxx@chinaren.com
You are currently subscribed to ntdev as: xxxxx@stratus.com
To unsubscribe send a blank email to $subst(‘Email.Unsub’)
Jingcao,
If your application is for a box that sits in the corner and does nothing
but take data from your card, there are games you can play. Peter
Viscarola, in his OSR driver seminar, tells of a special device driver they
wrote to (if I recall correctly) win some kind of performance benchmark
contest. The driver pretty much never left the DPC. So not only did the
driver have an excellent benchmark score, the cursor on the screen would not
move or even blink. Clearly this is not an acceptable thing for a
general-use card, but there are times when you gotta do what you gotta do.
-Evan
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Roddy, Mark
Sent: Tuesday, May 23, 2000 8:30 AM
To: NT Developers Interest List
Subject: [ntdev] RE: Question about the real time response!!!
I think there was a paper about average interrupt latency on NT
systems that
was published a year or two ago. I think also that it might have been from
Intel. You should do a web search. The worst case is of course
pretty horrid
and undoubtedly outside the requirement that your isr should never miss a
6ms interval. All that takes is a few concurrent interrupts at higher
priority with isrs that each consume a significant portion of the
6ms. Hmm…
perhaps the floppy disk driver would do it? NT is not a real time system,
and you have little or no control over the priority of your isr.
> -----Original Message-----
> From: Jingcao Hu [mailto:xxxxx@chinaren.com]
> Sent: Tuesday, May 23, 2000 3:04 AM
> To: NT Developers Interest List
> Subject: [ntdev] Question about the real time response!!!
>
>
> Hello Gurus,
> I have developed a PCI card which will continuously interrupt every
> 6ms, and it is asked that none of the interrupt should be missed.
> When I tested it with my driver on my HP LH3000 net server: PIII
> 533+128M ram, it runs perfectly well without missing any interrupts,
> at least till now.
> But now, my boss asked me to give him a theoretical estimation of the
> interrupt missing probability. I don’t know how to calculate it. How
> could I know in the worst case, how long will it take for my card
> interrupt to issue the isr routine of my driver? How to calculate the
> probability?
> Your help is highly appreciated.
>
>
>
>
>
> Best regards,
> Jingcao mailto:xxxxx@chinaren.com
>
>
>
> —
> You are currently subscribed to ntdev as: xxxxx@stratus.com
> To unsubscribe send a blank email to $subst(‘Email.Unsub’)
>
You are currently subscribed to ntdev as: xxxxx@pcu.net
To unsubscribe send a blank email to $subst(‘Email.Unsub’)
I remember that paper! Even found the hard copy and a link.
Nice title anyway:
“The Problem You’re Having May Not Be The Problem You
Think You’re Having: Results from a Latency Study of Windows NT”
http://www.research.microsoft.com/~mbj/papers/tr-98-29.html
-bk
Roddy, Mark wrote:
I think there was a paper about average interrupt latency on NT systems that
was published a year or two ago. I think also that it might have been from
Intel. You should do a web search. The worst case is of course pretty horrid
and undoubtedly outside the requirement that your isr should never miss a
6ms interval. All that takes is a few concurrent interrupts at higher
priority with isrs that each consume a significant portion of the 6ms. Hmm…
perhaps the floppy disk driver would do it? NT is not a real time system,
and you have little or no control over the priority of your isr.
> -----Original Message-----
> From: Jingcao Hu [mailto:xxxxx@chinaren.com]
> Sent: Tuesday, May 23, 2000 3:04 AM
> To: NT Developers Interest List
> Subject: [ntdev] Question about the real time response!!!
>
>
> Hello Gurus,
> I have developed a PCI card which will continuously interrupt every
> 6ms, and it is asked that none of the interrupt should be missed.
> When I tested it with my driver on my HP LH3000 net server: PIII
> 533+128M ram, it runs perfectly well without missing any interrupts,
> at least till now.
> But now, my boss asked me to give him a theoretical estimation of the
> interrupt missing probability. I don’t know how to calculate it. How
> could I know in the worst case, how long will it take for my card
> interrupt to issue the isr routine of my driver? How to calculate the
> probability?
> Your help is highly appreciated.
>
>
>
>
>
> Best regards,
> Jingcao mailto:xxxxx@chinaren.com