On Thu, Mar 23, 2000 at 04:09:15PM -0500, Michael B. Rash wrote:
> Suppose that I have a process that generates a timestamp every time it
> loops through some task, and assume that this process is not running with
> real time support. Is there any way to guarantee that the timestamping
> will be accurate to within some bound? That is, my task ends at some
> absolute time t0, and my timestamp gets assigned some short time t1 after
> t0 (if there is a context switch before the timestamp is assigned then the
> delay will be greater I guess). So, is there any way to bound t1-t0?
>
> My guess is that trying to _guarantee_ that t1-t0 < n for some n would
> be useless since my process could get swapped out with some higher
> priority process, or a bunch of interrupts happen, etc. But on _average_
> what would n be? It would be related to the processor speed, the machine
> load, and the jiffie that has been compiled into the machine correct?
No timing guarantee at all for non-realtime processes. Even for realtime
processes Linux doesn't provide a 100% guarantee as it only provides so
called soft realtime support unless you use RTlinux which also requires
special software for hard realtime.
Ralf
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