> : >Are there and patches/utilities/anything to measure interrupt latency
> : >under linux ?
> :
> : The easiest way to measure interrupt latency is with a signal generator
> : and an oscilloscope. No software solution is likely to give good results.
>
> I reall wish this wasn't the case because I would dearly love to be able to
> have interrupt latency as a benchmark test in lmbench. Are you sure there
> is no way to do this in software? What if you had some way to generate
> interrupts essentially continuously?
with performace counters/registers the following should be possible:
run a tight loop in user mode and store current time in memory (volatile variable).
add some code in kernel interupt handler to save current time in some area
(maybe for /proc/...) plus a copy of last user-mode time.
this gives interrupt entry delay.
for interrupt exit delay, user mode has to check for larger delays
between last and current time (e.g. > 10-20usec) and in this case
get a copy of kernel's time stamp from ISR just before exiting
from interrupt code...
Harald
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