[LEAPSECS] My FOSDEM slides
stenn at ntp.org
Sun Mar 1 17:25:36 EST 2015
Joseph Gwinn writes:
> On Sun, 01 Mar 2015 20:35:20 +0000, Harlan Stenn wrote:
> Once people get a system to work, they don't tend to go fixing things
> that ain't broke.
There's breakage they know about and breakage they don't know about...
>>> 2. Slide titled ""Possibilities for Future Improvements (2)": In the
>>> wish list for a kernel call to ask if the kernel runs UTC or TAI, a
>>> couple of issues come to mind. First, many systems set the GPS
>>> receiver to emit GPS System Time via NTP (and IRIG), so a GPS System
>>> Time option may be needed. Second, we often have the GPS (or PTP 1588)
>>> receiver to emit GPS System Time, but never share this with downstream
>>> servers, who are configured for UTC (but strangely the leap seconds
>>> never come). The difference between UTC and GPS System Time is handled
>>> in applications code. The reason for this approach is so that the bulk
>>> of the system is free from step discontinuities, and only the
>>> interfaces need deal with UTC.
>> This issue is also address by NTF's General Timestamp API, as
>> "timescale" is one of the data elements of this timestamp. We have
>> already done a proof-of-concept to get these timestamps used as the core
>> part of the kernel timekeeping API. There is clearly more work to be
>> done here. We know how to do this work, we just need technical and
>> financial support to make it happen.
> Great. Is this API a parallel to the named clock interface of POSIX,
> where the OS kernel vendor can add named clocks that are not in the
> POSIX standard - what is standardized is the mechanism for defining and
> using special purpose clocks unknown to POSIX.
I haven't looked, and my instant thought is that the POSIX named
clock interface could trivially use the GTSAPI. The timestamps provided
would include both a timescale and a "clock ID".
Harlan Stenn <stenn at ntp.org>
http://networktimefoundation.org - be a member!
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