Re: [PATCH v3 0/3] perf: User/kernel time correlation and event generation

[Arnd Bergmann]

On Monday 03 November 2014 17:11:53 John Stultz wrote:
> I've got some thoughts on what a possible interface that wouldn't be
> awful could look like, but I'm still hesitant because I don't really
> know if exposing this sort of data is actually a good idea long term.
 
I was also thinking (while working on an unrelated patch) we could use
a system call like

int clock_getoffset(clockid_t clkid, struct timespec *offs);

that returns the current offset between CLOCK_REALTIME and the
requested timebase. It is of course racy, but so is every use
of CLOCK_REALTIME. We could also use a reference other than
CLOCK_REALTIME that might be more stable, but passing two arbitrary
clocks as input would make this much more complex to implement.

	Arnd
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