Messages in this thread | | | Date | Tue, 11 Aug 1998 09:00:58 -0200 (GMT+2) | From | Paptis Ioannis <> | Subject | Re: interrupt latency |
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I don't care your list so somebody take out my e-mail address.
On Mon, 10 Aug 1998, Richard B. Johnson wrote:
> On Mon, 10 Aug 1998, 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 the Intel machines, you can. You can generate a software interrupt. > You have to make, perhaps, a dummy driver that operates in ring 0 (kernel > mode). > > This device could acquire an interrupt (IRQ) from the kernel. It could > also generate a software interrupt for the IRQ number (they are not the > same). The device could measure the time from which it generated a > software interrupt to the time its ISR was called by the kernel. > > This time would include all the software overhead, but not the hardware > overhead (which should be very, very much smaller than the software > overhead). The fact that the kernel will mask/ACK/unmask the hardware > controller(s) will not hurt the execution of the software interrupt. > > Now, that said, since all interrupts are handled the same except for > the very small interval for the cascade, you could just review the > generated assembly and calculate the execution times which might > be simpler than writing the dummy driver. Nevertheless, if the driver > was ismod-ed, and you could talk to it via ioctls (some new device > in /dev), you could have a useful tool. It might not be useful for > very long because I doubt that you could remove much code or improve > upon the interrupt handling very much. > > Cheers, > Dick Johnson > ***** FILE SYSTEM WAS MODIFIED ***** > Penguin : Linux version 2.1.115 on an i586 machine (66.15 BogoMips). > Warning : It's hard to remain at the trailing edge of technology. > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.altern.org/andrebalsa/doc/lkml-faq.html >
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