Implementation of High Precision Timer

Hello,

I need to implement a high precision timer for a network driver. I
need high resolution like µs or even ns - so much more presision than
using jiffies. Unfortunately I can't find some code examples for
implementing it in kernel mode.

Can anybody help me with this - send me code examples or give me some
useful links ?

Thanks a lot!

Thilo

(E-Mail Removed) writes:

>Hello,

>I need to implement a high precision timer for a network driver. I
>need high resolution like =B5s or even ns - so much more presision than
>using jiffies. Unfortunately I can't find some code examples for
>implementing it in kernel mode.

You cannot do it. There are far too many thngs in a multitasking operating
system which can vary the response time of the system. A few usec is
possible, but hard. Better than that I do ot think so.
If you want to build a hardware clock then maybe it is possible.

Now perhaps if you told us what theproblem was rather than how you were
going to solve theproblem someone could give some advice as to how to do
it.


>Can anybody help me with this - send me code examples or give me some
>useful links ?

>Thanks a lot!

>Thilo

bieradler wrote:

> I need to implement a high precision timer for a network driver. I
> need high resolution like µs or even ns - so much more presision than
> using jiffies. Unfortunately I can't find some code examples for
> implementing it in kernel mode.

Linux Device Drivers, Third Edition
http://lwn.net/Kernel/LDD3/

Chapter 7: Time, Delays, and Deferred Work
http://lwn.net/images/pdf/LDD3/ch07.pdf

Real-Time Linux Wiki
http://rt.wiki.kernel.org/index.php/Main_Page

hrtimers (already in mainline)
http://www.tglx.de/hrtimers.html

Regards.

Boon wrote:

> bieradler wrote:
>
>> I need to implement a high precision timer for a network driver. I
>> need high resolution like µs or even ns - so much more presision than
>> using jiffies. Unfortunately I can't find some code examples for
>> implementing it in kernel mode.
>
> Linux Device Drivers, Third Edition
> http://lwn.net/Kernel/LDD3/
>
> Chapter 7: Time, Delays, and Deferred Work
> http://lwn.net/images/pdf/LDD3/ch07.pdf
>
> Real-Time Linux Wiki
> http://rt.wiki.kernel.org/index.php/Main_Page
>
> hrtimers (already in mainline)
> http://www.tglx.de/hrtimers.html

http://elinux.org/High_Resolution_Timers

Hello thanks for your help!

Some more information about my problem, so maybe someone has the right
solution for my problem:

I need to program a driver for a hardware device which doesn't support
interrupts. So i have to periodically poll the register contents of
the device (connected via PCI). At the moment I use a timer therfore
which is based on jiffies - but is much to slow. The polling cycles
are about 2-4 ms.

I looked at the PTPD protocol which uses high resolution timers. But I
can't use this code in kernel space.

So if anybody use an idea i would be very pleased!!!

thanks a lot!

bieradler wrote:

> I need to program a driver for a hardware device which doesn't support
> interrupts. So i have to periodically poll the register contents of
> the device (connected via PCI). At the moment I use a timer therfore
> which is based on jiffies - but is much to slow. The polling cycles
> are about 2-4 ms.

If you set HZ to 1000, then the PIT will fire every millisecond.

I've played with the -hrt infrastructure on x86. My app would sleep
for 250 microseconds, then wake up, in an infinite loop.