On 12/21/2009 04:16 AM, Nikita V. Youshchenko wrote: >> On 12/18/2009 11:56 AM, Vladimir Cotfas wrote: >>> All, >>> >>> I have a a driver that must process an interrupt every 100 uS without >>> missing any. I am having latency issues and I am looking for some help >>> debugging my problem. >> >> You'll probably never get this working reliably with the RT kernel. >> Latencies are more deterministic with the RT kernel but slightly higher. >> You'll have better luck with a vanilla kernel running your app in run >> level 4. And then even better luck running on an SMP machine isolating >> your process and IRQ to a single processor. And stay away from the VGA >> console. You have better luck with faster hardware too. > > We have seen <20us avg latencies on RT kernel on slower powerpc-based SoC. > > The only problem is that sometimes we got single-shot latency >150 us - > that happened when sched tick was running for >100 us with interrupts > disabled. > Averages are one thing. Guaranteeing he doesn't miss _any_ and still has time to do whatever he needs to do before the next one, is different. Local timer interrupts alone are enough to kill ya. Mark -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
