Messages in this thread | | | Date | Wed, 6 Aug 2008 15:20:10 -0700 | From | "Ray Lee" <> | Subject | Re: HZ from userspace |
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On Wed, Aug 6, 2008 at 3:16 PM, Ray Lee <ray-lk@madrabbit.org> wrote: > On Wed, Aug 6, 2008 at 3:07 PM, Piotr Jaroszyński > <p.jaroszynski@gmail.com> wrote: >>>> I want to be able to convert starttime from /proc/#/stat to absolute >>>> time and it seems that I need HZ to do that as it is measured in >>>> jiffies. How can I get HZ? I have seen some discussion about this but >>>> haven't found a definite answer. procps is using some hacks do it and >>>> I would prefer to avoid them. >>>> I only need a solution for modern kernels, say 2.6.20+ if that matters. >>> >>> `man sysconf`, in particular you want sysconf(_SC_CLK_TCK). >> >> manpage says it's obsolete and i read in some discussion that it only >> returns the default and not the real HZ used. > > I believe the claim that it's out of date is out of date. manpages > 3.0.1 has an update to this, according to a message I saw on this list > a month or so ago. > > Regardless, the fields you're reading should all be showing USER_HZ > which is fixed at 100 per second regardless of the underlying kernel > HZ parameter. > > Try it. >
Here's the latest proc(5) man page from June 25, 2008. Look for _SC_CLK_TCK about a third of the way down.
http://www.kernel.org/doc/man-pages/online/pages/man5/proc.5.html
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