Thierry MARTIN <[EMAIL PROTECTED]> writes: >Hi All,
>Sorry for beeing too enthousiastic about my initial test... >I launched another test with clocksource=acpi_pm, on the same machine. >The results are bad now (> 500ms in a few hours). >FYI, the command I launched: ># rm /etc/adjtime; ># ntpdate ntp.cines.fr; ># hwclock --systohc; ># adjtimex -a >Then I watch: ># ntpdate -q ntp.cines.fr >Keeping a linux system with the correct time without any external >synchronisation really seems hard... Yes. YOu expected something else? If you use chrony, you can enter in the time by hand now and then again in 8 hours. chrony will use that data to estimate the drift of the oscillator and use that drift info to try to keep the clock on better time. You CANNOT expect a PC oscillator to keep good time without drift compensation. They were never designed for that. Note that 1 sec in 10 hours is a drift rate of only 30PPM. which is well within the error budget of most crystals. With hand setting you can probably reduce that by a factor of 10 but not much better due to temp variations, etc. >Best regards >Thierry. >Thierry MARTIN a écrit : >> Oups? >> >> If I understand your post, tsc is the same as acpi_pm ? >> >> Was I just a lucky guy with this config? >> >> (:- You've just killed my enthousiasm ... :-) >> >> >> >> David Woolley a écrit : >>> Thierry MARTIN wrote: >>> >>>> I have been trying acpi_pm clocksource for a few days now and the >>>> results are quite good :-). >>>> >>>> The time drift is less than 1s per day (I would even say less that >>>> 500ms but this has to be confirmed) which is much better than the >>>> default config with tsc (>2s /day). >>> >>> It's almost certain that the same hardware time source is used for >>> both, so discrepancies are likely to be attributable to software >>> issues (although those may include problems in calibrating the >>> frequency of various sources empirically, rather than by knowing how >>> they derive from the common source).
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