Messages in this thread |  | | | Date | Mon, 8 Mar 2010 19:25:07 -0800 | | Subject | Re: [PATCHv2 0/6] pps: time synchronization over LPT | | From | john stultz <> |
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On Wed, Feb 24, 2010 at 4:28 AM, Alexander Gordeev <lasaine@lvk.cs.msu.su> wrote: > This patchset is tested against the vanilla 2.6.32.9 kernel. But we are > actually using it on 2.6.31.12-rt20 rt-preempt kernel most of the time. > Also there is a version which should be applied on top of LinuxPPS out > of tree patches (i.e. all clients and low-level irq timestamps stuff). > Those who are interested in other versions of the patchset can find > them in my git repository: > http://lvk.cs.msu.su/~lasaine/timesync/linux-2.6-timesync.git > > There is one problem however: hardpps() works bad when used on top > of 2.6.33-rc* with CONFIG_NO_HZ enabled. The reason for this is commit > a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601. Without it hardpps() is able > to sync to 1us precision in about 10 seconds. With it
Uh. Not sure I see right off why the logarithmic time accumulation would give you troubles. Its actually there to try to fix a couple of NTP issues that cropped up when the accumulation interval was pushed out to 2HZ with CONFIG_NO_HZ.
Do you have any extra insight here as to whats going on with your code? The only thing I could guess would be second_overflow() is happening closer to the actual overflow, but maybe less regularly? But again, I'm not sure how this would be drastically different then before with the 2HZ accumulation period.
thanks -john
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