Clock resolution / RT preemption

Clock resolution / RT preemption

[greg]

Hi folks,

I'm looking for a timer resolution lower than 1 ms (and monotonic clock 
rate) destined to be used with some network code running on x86 
platforms. Would you please provide me with informations about how to 
get/implement this.

AFAIK, there's a "high resultion timer" patch hanging around, but 
there's not much informations with regard to portability (specific 
hardware requirements ?), scalability, integration with RT patches.
I understand the POSIX 1003.1b Clocks and Timers system calls are not 
fully available within the linux kernel (and libc ?), am I right on that ?

One more question : I believe Ingo's preemption patch run 
timers/interrupt handlers within kernel threads, how should I assign 
specific priority to address my goals without compromising system 
stability ?

Re: Clock resolution / RT preemption

[George Anzinger]

greg wrote:
> Hi folks,
> 
> I'm looking for a timer resolution lower than 1 ms (and monotonic clock 
> rate) destined to be used with some network code running on x86 
> platforms. Would you please provide me with informations about how to 
> get/implement this.
> 
> AFAIK, there's a "high resultion timer" patch hanging around, but 
> there's not much informations with regard to portability (specific 
> hardware requirements ?), scalability, integration with RT patches.
> I understand the POSIX 1003.1b Clocks and Timers system calls are not 
> fully available within the linux kernel (and libc ?), am I right on that ?

On the HRT web site (see signature) there is a CVS repository.  In there 
is a special version for the RT kernel.  As to porting it to other 
archs, have a look at the include/linux/hrtimer.h file.  It has (or 
should have) all you need to know.  Please pass back any port you do.
> 
> One more question : I believe Ingo's preemption patch run 
> timers/interrupt handlers within kernel threads, how should I assign 
> specific priority to address my goals without compromising system 
> stability ?

Carefully :)

-- 
George Anzinger   george@mvista.com
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/