Messages in this thread | | | Date | Tue, 31 Aug 2004 12:27:23 -0700 | From | George Anzinger <> | Subject | Re: [PATCH] Re: boot time, process start time, and NOW time |
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Tim Schmielau wrote: > On Mon, 30 Aug 2004, john stultz wrote: > > >>On Mon, 2004-08-30 at 16:00, Tim Schmielau wrote: >> >>>George, please excuse my lack of understanding. What again where the >>>precise reasons to have an ntp-corrected uptime? >> >>Ah, here's the thread with the first mention of it that I could find. >> >>http://www.uwsg.iu.edu/hypermail/linux/kernel/0306.1/1471.html
As I recall the problem was that jiffies since boot was being converted to get uptime base on 1/HZ = 1 jiffie. Since it is really not quite that, there was an error. Using clock_monotonic seemed like the right answer as it eliminated the error AND made the result consistant with get_clock(CLOCK_MONOTONIC,..).
The alternate answer is, of course, to directly convert the elapsed jiffies. The main problem with this is that this can be a BIG number and, therefor, the math needs to be carefully. And, of course, it is inconsistant with get_clock(), but that is a new interface...
George > > > Ah, it seems George indeed did the patch because of these problems: > > http://www.uwsg.iu.edu/hypermail/linux/kernel/0306.1/1641.html > > However, the actual reason were just missing wall_to_monotonic > initializations: > > http://www.uwsg.iu.edu/hypermail/linux/kernel/0306.2/1330.html > > This was fixed in mainline: > > http://linus.bkbits.net:8080/linux-2.5/cset%403f0e60dcpIosK3b5_uJ-aD9Mare17w > > Tim >
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
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