Re: Accessing monotonic clock from modules

[Chris Friesen <cfriesen@nortel.com>]

Arjan van de Ven wrote:
> On Thu, 2005-06-02 at 07:46 -0600, Chris Friesen wrote:

>>For ourselves we implemented an clock interface for a limited subset of 
>>architectures that provides a fast timestamp in kernel and userspace.
>>
>>Basically it has one call to return a 64-bit timestamp, and another call 
>>to tell you how fast the clock is ticking.
> 
> 
> hmm this is tricky if cpufreq actually varies cpu speeds... you would
> need to not cache the "how fast it ticks" for too long.

Luckily we didn't need to deal with that.

In order to use the fast versions with varying frequency you'd need some 
kind of notification to all users when the frequency changes.

Alternately, on architectures where clock_gettime doesn't require the 
overhead of a syscall, you could just use that.

Chris