Re: 2.6.4 timer and helper functions

George Anzinger
2005-05-19T00:39:57Z

kernel@wired-net.gr wrote:
> Hi all,
> i am running a 2.6.4 kernel on my system , and i am playing a little bit
> with kernel time issues and helper functions,just to understand how the
> things really work.
> While doing that on my x86 system and loaded a module from LDD 3rd
> edition,jit.c, which uses a dynamic /proc file to return textual
> information.
> The info that returns is in this format and uses the kernel functions
> ,do_gettimeofday,current_kernel_time and jiffies_to_timespec.
> The output format is:
> 0x0009073c 0x000000010009073c 1116162967.247441
> 1116162967.246530656 591.586065248
> 0x0009073c 0x000000010009073c 1116162967.247463
> 1116162967.246530656 591.586065248
> 0x0009073c 0x000000010009073c 1116162967.247476
> 1116162967.246530656 591.586065248
> 0x0009073c 0x000000010009073c 1116162967.247489
> 1116162967.246530656 591.586065248
> where the first two values are the jiffies and jiffies_64.The next two are
> the do_gettimeofday and current_kernel_time and the last value is the
> jiffies_to_timespec.This output text is "recorded" after 16 minutes of
> uptime.Shouldnt the last value be the same as uptime.I have attached an
> output file from the boot time until the time the function resets the
> struct and starts count from the beggining.Is this a bug or i am missing
> sth here???

You are assuming that jiffies starts at zero at boot time. This is clearly not
so even from your print outs. (It starts at a value near overflow of the low
order 32-bits to flush out problems with the roll over.)
>
--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/