roland Tollenaar wrote: > Hi > >> The latency killers: >> - SMI: check dmesg to see if you get a warning saying that an >> SMI-enabled chipset was detected. If yes, > Yes get this message. > >> read the TROUBLESHOOTING. If > Done what it says here. No change. My latency is also less than 100 us > so this is probably not the problem. Tried anyway but as mentioned, no > difference. > >> - USB: disable legacy USB in BIOS configuration, sometimes it is not > My BIOS settings do not allow me to switch off the USB legacy. At > least I cannot find the place where this is to be done. > > >> enough, and you have to _enable_ USB in kernel configuration, and load >> the USB modules (that is at least uhci-hcd, ohci-hcd, ehci-hcd and >> usbcore) so that they disable BIOS legacy USB emulation. > These ARE enabled. > >> - X-window: if you see high latencies only when the X server is running, >> the X-server is probably causing them. A workaround is proposed in the >> TROUBLESHOOTING file. > Ran latency without X running. No difference. > >> >> In case all that fails, enable the I-pipe tracer, run latency with the >> -f option, and check /proc/ipipe/trace/frozen once you observed the high >> latency in latency. > Have done this and attached the result. I have looked at it myself but > cannot interpret the meaning. > > A bit of help would be appreciated.
Two conclusions: - You are running your kernel as i586 without TSC support - suboptimal, costs you a few micros. - The reported latency perfectly matches the trace, nothing pathological there. The trace looks like this: Timer fired, measurement task woken up, two interrupts squeeze themselves between wakeup and time stamp acquisition. All sane. Jan
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