Philippe Gerum a écrit : > On Wed, 2007-10-17 at 17:46 +0200, CHABAL David wrote: >> Philippe Gerum a écrit : >>> On Wed, 2007-10-17 at 16:52 +0200, CHABAL David wrote: >>>>> Grmmff... I think the PIC on this box has some deep troubles; please try >>>>> this patch, in replacement of the previous ipipe_trace_special >>>>> instrumentation: >>>>> >>>> RTD| 8.348| 10.387| 43.647| 0| 6.098| >>>> 80.440 >>>> ---|------------|------------|------------|--------|------------------------- >>>> RTS| 6.098| 10.020| 80.440| 0| 00:17:20/00:17:20 >>>> [EMAIL PROTECTED] bin]# >>>> >>>> >>>> IRQ handling takes 17µs in the worst case. >>>> >>>> It takes a long time to write 3 poor bytes... >>>> >>> Indeed. Each outb to the ISA bus should be somewhere in the 1-2.5 us >>> range depending on the hw, maybe a bit higher in case of contention, but >>> not that much. >>> >>>> May be is it a SMI problem ??? (Globally disable SMI is on) >>>> >>> It's less likely with an ICH-2 chipset. >>> >>> I see that CONFIG_IDEDMA_PCI_AUTO is disabled. Any reason not to use PCI >>> DMA when available for IDE drives with your hw? >>> >> I read this about DMA: >> http://www.rtai.dk/cgi-bin/gratiswiki.pl?DMA_And_Jitter >> > > As usual, usage of DMA in real-time situations is a trade-off, and > should be evaluated within the context of the hw at hand. DMA does bus > mastering, but OTOH, forcing PIO raises native Linux latencies, which > also has some drawbacks for real-time kernels implementing RT/non-RT > mode transitions for tasks like Xenomai and RTAI do. For this reason, > you may want to try switching PCI DMA on for your platform, until it > does prove bad latency-wise. > I tested it but the results are almost the same.
I will try to upgrade my kernel to the 2.6.22 and to test again. David _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
