Messages in this thread | | | Date | Tue, 11 Aug 1998 09:49:11 +0200 | From | Harald Koenig <> | Subject | Re: interrupt latency |
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On Aug 10, Larry McVoy wrote:
> : >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 -- All SCSI disks will from now on ___ _____ be required to send an email notice 0--,| /OOOOOOO\ 24 hours prior to complete hardware failure! <_/ / /OOOOOOOOOOO\ \ \/OOOOOOOOOOOOOOO\ \ OOOOOOOOOOOOOOOOO|// Harald Koenig, \/\/\/\/\/\/\/\/\/ Inst.f.Theoret.Astrophysik // / \\ \ koenig@tat.physik.uni-tuebingen.de ^^^^^ ^^^^^
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