Messages in this thread | | | Date | Fri, 24 Mar 2000 04:10:30 +0100 | From | Ralf Baechle <> | Subject | Re: general timing question |
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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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