On Sun, 26 Jan 2014, Michael Haberler wrote: > Date: Sun, 26 Jan 2014 17:40:19 +0100 > From: Michael Haberler <[email protected]> > To: Peter C. Wallace <[email protected]>, > EMC developers <[email protected]> > Subject: Re: [Emc-developers] reports on rt-preempt / latency-test: max jitter > going down > > > Am 26.01.2014 um 17:28 schrieb Peter C. Wallace <[email protected]>: > >> On Sun, 26 Jan 2014, Michael Haberler wrote: >> >>> Date: Sun, 26 Jan 2014 09:59:52 +0100 >>> From: Michael Haberler <[email protected]> >>> To: EMC developers <[email protected]> >>> Subject: Re: [Emc-developers] reports on rt-preempt / latency-test: max >>> jitter >>> going down >>> could the folks observing this behaviour please run the following commands >>> on their systems: >>> >>> cat /sys/devices/system/clocksource/clocksource0/available_clocksource >>> >>> cat /sys/devices/system/clocksource/clocksource0/current_clocksource >>> >>> background: Answer 2 of: >>> http://stackoverflow.com/questions/5930621/problem-of-understanding-clock-gettime >>> >>> thanks! >> >> >> cat /sys/devices/system/clocksource/clocksource0/available_clocksource >> tsc acpi_pm >> >> cat /sys/devices/system/clocksource/clocksource0/current_clocksource >> tsc > > hm, I would have expected to find 'hpet' there (see also link below) > maybe for some reason HPET isnt enabled in the kernel so not settable > > (is that by chance my howegrown 3.1x-mah rt-preempt kernel..?)
Yes > > >> >> >> I changed the clocksource to acpi_pm but the error remains > > acpi_pm is probably the worst of all in terms of resolution, 3.58Mhz: > http://stackoverflow.com/questions/7987671/what-is-the-acpi-pm-linux-clocksource-used-for-what-hardware-implements-it > > it's probably a good idea to figure out the best clock source, and make sure > in the startup phase it's actually selected (assuming this is related at all) > >> One interesting thing is that the error is periodic with a ~4 second period >> (like an uncaught 32 bit ns count wrap) > > hm, thats an interesting observation. Need to read the timedelta and > rtapi_time code once more to see if there's something smelly. > > does that 4 second period show up with either clock source just alike? if so, > this would suggest the clock source not be the cause Yes, same ~4 second period with either clock source, I HAL 'scoped the baddelta staircase and its 4.3 seconds as you would expect with a uncaught 32 bit wrap > > I should be next to real hardware soon > > thanks! > > - Michael > >> >> >> >> >>> >>> - Michael >>> >>> >>> Am 25.01.2014 um 17:03 schrieb Michael Haberler <[email protected]>: >>> >>>> >>>> Peter Wallace kindly help to locate the error, it is rtapi_get_time() >>>> going backwards occasionally on rt-preempt, suggesting the cause is this >>>> function: >>>> >>>> >>>> https://github.com/mhaberler/linuxcnc/blob/e3de5bb74857bbd9935c1a1d1f031a0558ca0f85/src/rtapi/rtapi_time.c#L166 >>>> >>>> this cause the 'del' variable in >>>> https://github.com/mhaberler/linuxcnc/blob/e3de5bb74857bbd9935c1a1d1f031a0558ca0f85/src/hal/components/timedelta.comp >>>> to become negative at times, causing the decreasing jitter >>>> >>>> no fix yet, but we know where to look >>>> >>>> -m >>>> >>>> >>>> Am 25.01.2014 um 08:43 schrieb Michael Haberler <[email protected]>: >>>> >>>>> Reading back on IRC I found hints at rt-preempt ubc3 builds showing the >>>>> max latency going down occasionally. >>>>> >>>>> Please: >>>>> >>>>> 1. report the exact kernel version, in particular if this is stock debian >>>>> rt-preempt kernel. >>>>> 2. check if ntp is running or not, i.e. the output of 'ps ax|grep ntp' >>>>> 3. If yes, please stop the ntp demon with 'sudo /etc/init.d/ntp stop' or >>>>> equivalent >>>>> 4. Re-run latency-test after ntp is stopped. Does the problem reoccur? >>>>> 5. Please report your results using the ubc issue tracker as mentioned >>>>> here >>>>> http://static.mah.priv.at/public/html/common/UnifiedBuild.html#_issue_tracker >>>>> , for this issue: https://github.com/zultron/linuxcnc/issues/72 >>>>> >>>>> background: there is a chance that the issue is related to the behavior >>>>> described here, in particular the subtle difference between >>>>> CLOCK_MONOTONIC and CLOCK_MONOTONIC_RAW: >>>>> >>>>> http://stackoverflow.com/questions/3657289/linux-clock-gettimeclock-monotonic-strange-non-monotonic-behavior >>>>> http://markmail.org/thread/54bb663vi47kjxnu >>>>> >>>>> - Michael >>>>> >>>>> >>>>> >>>>> ------------------------------------------------------------------------------ >>>>> CenturyLink Cloud: The Leader in Enterprise Cloud Services. >>>>> Learn Why More Businesses Are Choosing CenturyLink Cloud For >>>>> Critical Workloads, Development Environments & Everything In Between. >>>>> Get a Quote or Start a Free Trial Today. >>>>> http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk >>>>> _______________________________________________ >>>>> Emc-developers mailing list >>>>> [email protected] >>>>> https://lists.sourceforge.net/lists/listinfo/emc-developers >>>> >>>> >>>> ------------------------------------------------------------------------------ >>>> CenturyLink Cloud: The Leader in Enterprise Cloud Services. >>>> Learn Why More Businesses Are Choosing CenturyLink Cloud For >>>> Critical Workloads, Development Environments & Everything In Between. >>>> Get a Quote or Start a Free Trial Today. >>>> http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk >>>> _______________________________________________ >>>> Emc-developers mailing list >>>> [email protected] >>>> https://lists.sourceforge.net/lists/listinfo/emc-developers >>> >> >> Peter Wallace >> Mesa Electronics >> >> (\__/) >> (='.'=) This is Bunny. 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