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SubjectAnyone else interested in a high-precision monotonic counter?

Has anyone ever considered including a microsecond-precision
monotonically-increasing counter in the kernel? This would allow for
easy timing of alarms and such by using absolute values of when the
alarm should expire rather than a list of deltas from previous alarms.

The thing I have in mind would store a value something like "xtime"
(maybe call it "ytime"?) in the kernel. This value would be initialized
to zero on startup, and would be incremented at the same time as
"xtime". However, while "xtime" reflects adjustments to the actual
system time (settimeofday(), date, ntp, etc.), this value would not.
Finally, it would be accessed with a system call essentially identical
to sys_gettimeofday(), only it would access "ytime" instead of "xtime"
before going down and getting the microseconds from the RTC.

This doesn't seem to me as though it would be all that tricky to add,
and I could see it being very useful in providing a timing source that
is guaranteed to a) be accurate to microseconds and b) never go
backwards.


Chris

--
Chris Friesen | MailStop: 043/33/F10
Nortel Networks | work: (613) 765-0557
3500 Carling Avenue | fax: (613) 765-2986
Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com
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